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Background: Recent observational studies in the United States indicated live attenuated influenza vaccine (LAIV) was less effective in children against clinical influenza infection caused by A(H1N1)pdm09 relative to inactivated influenza vaccine (IIV). During the 2013-2014 influenza season, we conducted an observational study among children aged 5-17 years to compare serologic responses to LAIV and IIV and explore factors associated with vaccine failure., Methods: One hundred and sixty-one children received one dose of trivalent IIV or quadrivalent LAIV according to parental preference. Baseline and postvaccination serum samples were tested with hemagglutination inhibition (HI) assays against vaccine reference strains. Geometric mean titers (GMT), geometric mean fold rise (GMFR), seroconversion, and seroprotection (HI titer ≥ 40) were used to assess response to vaccine. Active surveillance for acute respiratory illness was conducted during the influenza season and influenza cases were confirmed by reverse transcription polymerase chain reaction (RT-PCR). Logistic regression was used to examine the association between vaccine type and vaccine failure., Results: LAIV and IIV recipients were similar with respect to demographics and baseline GMT for each vaccine strain. RT-PCR confirmed influenza (vaccine failure) occurred in 8 (13%) of 62 LAIV recipients and 3 (3%) of 99 IIV recipients (p = .02). Postvaccination GMFR for A(H1N1)pdm09 was higher for IIV vs LAIV receipt (GMFR 3.3 vs. 0.8, p < .0001). Postvaccination titers against A(H1N1)pdm09 were ≥40 for 91% and 44% of IIV and LAIV recipients, respectively (p < .0001). Among 13 IIV and 18 LAIV recipients with seronegative baseline titer against A(H1N1pdm09), 54% and 0% seroconverted, respectively. LAIV receipt was the only factor associated with A(H1N1)pdm09 vaccine failure in the age-adjusted multivariable model (odds ratio 4.5, 95% CI 1.1-18.2)., Conclusion: Receipt of LAIV generated minimal HI antibody response in children, including among those seronegative at baseline. LAIV recipients had significant increased risk of A(H1N1)pdm09 infection compared to IIV recipients., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In the United States, annual vaccination against seasonal influenza is recommended for all persons aged ≥6 months (1). During each influenza season since 2004-05, CDC has estimated the effectiveness of seasonal influenza vaccine to prevent laboratory-confirmed influenza associated with medically attended acute respiratory illness (ARI). This report uses data from 4,562 children and adults enrolled in the U.S. Influenza Vaccine Effectiveness Network (U.S. Flu VE Network) during November 2, 2017-February 3, 2018. During this period, overall adjusted vaccine effectiveness (VE) against influenza A and influenza B virus infection associated with medically attended ARI was 36% (95% confidence interval [CI] = 27%-44%). Most (69%) influenza infections were caused by A(H3N2) viruses. VE was estimated to be 25% (CI = 13% to 36%) against illness caused by influenza A(H3N2) virus, 67% (CI = 54%-76%) against A(H1N1)pdm09 viruses, and 42% (CI = 25%-56%) against influenza B viruses. These early VE estimates underscore the need for ongoing influenza prevention and treatment measures. CDC continues to recommend influenza vaccination because the vaccine can still prevent some infections with currently circulating influenza viruses, which are expected to continue circulating for several weeks. Even with current vaccine effectiveness estimates, vaccination will still prevent influenza illness, including thousands of hospitalizations and deaths. Persons aged ≥6 months who have not yet been vaccinated this season should be vaccinated., Competing Interests: No conflicts of interest were reported.

Background: In the 2015-2016 season, quadrivalent live attenuated influenza vaccine (LAIV) and both trivalent and quadrivalent inactivated influenza vaccine (IIV) were available in the United States., Methods: This study, conducted according to a test-negative case-control design, enrolled children aged 2-17 years presenting to outpatient settings with fever and respiratory symptoms for <5 days at 8 sites across the United States between 30 November 2015 and 15 April 2016. A nasal swab was obtained for reverse-transcriptase polymerase chain reaction (RT-PCR) testing for influenza, and influenza vaccination was verified in the medical record or vaccine registry. Influenza vaccine effectiveness (VE) was estimated using a logistic regression model., Results: Of 1012 children retained for analysis, most children (59%) were unvaccinated, 10% received LAIV, and 31% received IIV. Influenza A (predominantly antigenically similar to the A/California/7/2009 strain) was detected in 14% and influenza B (predominantly a B/Victoria lineage) in 10%. For all influenza, VE was 46% (95% confidence interval [CI], 7%-69%) for LAIV and 65% (48%-76%) for IIV. VE against influenza A(H1N1)pdm09 was 50% (95% CI, -2% to 75%) for LAIV and 71% (51%-82%) for IIV. The odds ratio for vaccine failure with RT-PCR-confirmed A(H1N1)pdm09 was 1.71 (95% CI, 0.78-3.73) in LAIV versus IIV recipients., Conclusions: LAIV and IIV demonstrated effectiveness against any influenza among children aged 2-17 years in 2015-2016. When compared to all unvaccinated children, VE against influenza A(H1N1)pdm09 was significant for IIV but not LAIV., Clinical Trials Registration: NCT01997450., (© The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America.)

Background: Antibodies to measles, mumps, and rubella decline 3% per year on average, and have a high degree of individual variation. Yet, individual variations and differences across antigens are not well understood. To better understand potential implications on individual and population susceptibility, we reanalyzed longitudinal data to identify patterns of seropositivity and persistence., Methods: Children vaccinated with the second dose of measles, mumps, rubella vaccine (MMR2) at 4-6 years of age were followed up to 12 years post-vaccination. The rates of antibody decline were assessed using regression models, accounting for differences between and within subjects., Results: Most of the 302 participants were seropositive throughout follow-up (96% measles, 88% mumps, 79% rubella). The rate of antibody decline was associated with MMR2 response and baseline titer for measles and age at first dose of MMR (MMR1) for rubella. No demographic or clinical factors were associated with mumps rate of decline. One month post-MMR2, geometric mean titer (GMT) to measles was high (3892 mIU/mL), but declined on average 9.7% per year among those with the same baseline titer and <2-fold increase post-MMR2. Subjects with ≥2-fold experienced a slower decline (≤7.4%). GMT to rubella was 149 one month post-MMR2, declining 2.6% and 5.9% per year among those who received MMR1 at 12-15 months and >15 months, respectively. GMT to mumps one month post-MMR2 was 151, declining 9.2% per year. Only 14% of subjects had the same persistence trends for all antigens., Conclusions: The rate of antibody decay varied substantially among individuals and the 3 antigen groups. A fast rate of decline coupled with high variation was observed for mumps, yet no predictors were identified. Future research should focus on better understanding waning titers to mumps and its impacts on community protection and individual susceptibility, in light of recent outbreaks in vaccinated populations., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Influenza vaccination may provide a "back-boost" to antibodies against previously encountered strains. If the back-boost effect is common, this could allow more aggressive vaccine updates, as emerging variants would be expected to both elicit de-novo responses and boost pre-existing responses against recently circulating strains. Here we used the emergence of an antigenically novel A(H3N2) strain to determine whether an antigenically updated vaccine boosted antibodies against historical strains., Methods: We performed hemagglutination-inhibition (HI) assays on pre- and post-vaccination sera from 124 children 5-17 years old who received 2015-2016 inactivated influenza vaccine, containing an antigenically updated A(H3N2) strain. We evaluated the mean fold increase in HI titer against both the 2015-2016 vaccine strain and representative strains from two prior antigenic clusters. Factors associated with post-vaccination titers against historical strains were evaluated using linear regression, adjusting for baseline titer., Results: Geometric mean titers against each antigen examined increased significantly after vaccination (P < .0001). Mean fold increase was 3.29 against the vaccine strain and 1.22-1.46 against historical strains. Response to vaccine strain was associated with increased post-vaccination titers against historical strains., Conclusions: A vaccine containing an antigenically novel A(H3N2) strain modestly boosted antibody responses against historical influenza strains in children., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

On October 20, 2017, Zoster Vaccine Recombinant, Adjuvanted (Shingrix, GlaxoSmithKline, [GSK] Research Triangle Park, North Carolina), a 2-dose, subunit vaccine containing recombinant glycoprotein E in combination with a novel adjuvant (AS01 B ), was approved by the Food and Drug Administration for the prevention of herpes zoster in adults aged ≥50 years. The vaccine consists of 2 doses (0.5 mL each), administered intramuscularly, 2-6 months apart (1). On October 25, 2017, the Advisory Committee on Immunization Practices (ACIP) recommended the recombinant zoster vaccine (RZV) for use in immunocompetent adults aged ≥50 years., Competing Interests: No conflicts of interest were reported.

Background: In addition to preventing hospitalizations and deaths due to influenza, influenza vaccination programs can reduce the burden of outpatient visits for influenza. We estimated the incidence of medically-attended influenza at three geographically diverse sites in the United States, and the cases averted by vaccination, for the 2013/14 through 2015/16 influenza seasons., Methods: We defined surveillance populations at three sites from the United States Influenza Vaccine Effectiveness Network. Among these populations, we identified outpatient visits laboratory-confirmed influenza via active surveillance, and identified all outpatient visits for acute respiratory illness from healthcare databases. We extrapolated the total number of outpatient visits for influenza from the proportion of surveillance visits with a positive influenza test. We combined estimates of incidence, vaccine coverage, and vaccine effectiveness to estimate outpatient visits averted by vaccination., Results: Across the three sites and seasons, incidence of medically attended influenza ranged from 14 to 54 per 1000 population. Incidence was highest in children aged 6 months to 9 years (33 to 70 per 1000) and lowest in adults aged 18-49 years (21 to 27 per 1000). Cases averted ranged from 9 per 1000 vaccinees (Washington, 2014/15) to 28 per 1000 (Wisconsin, 2013/14)., Discussion: Seasonal influenza epidemics cause a considerable burden of outpatient medical visits. The United States influenza vaccination program has caused meaningful reductions in outpatient visits for influenza, even in years when the vaccine is not well-matched to the dominant circulating influenza strain., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: Population-based estimates of influenza-associated outpatient visits including both pandemic and interpandemic seasons are uncommon. Comparisons of such estimates with laboratory-confirmed rates of outpatient influenza are rare., Objective: To estimate influenza-associated outpatient visits in 6 US integrated healthcare delivery organizations enrolling ~7.7 million persons., Methods: Using negative binomial regression methods, we modeled rates of influenza-associated visits with ICD-9-CM-coded pneumonia or acute respiratory outpatient visits during 2001-10. These estimated counts were added to visits coded specifically for influenza to derive estimated rates. We compared these rates with those observed in 2 contemporaneous studies recording RT-PCR-confirmed influenza outpatient visits., Results: Outpatient rates estimated with pneumonia visits were 39 (95% confidence interval [CI], 30-70) and 203 (95% CI, 180-240) per 10 000 person-years, respectively, for interpandemic and pandemic seasons. Corresponding rates estimated with respiratory visits were 185 (95% CI, 161-255) and 542 (95% CI, 441-823) per 10 000 person-years. During the pandemic, children aged 2-17 years had the largest increase in rates (when estimated with pneumonia visits, from 64 [95% CI, 50-121] to 381 [95% CI, 366-481]). Rates estimated with pneumonia visits were consistent with rates of RT-PCR-confirmed influenza visits during 4 of 5 seasons in 1 comparison study. In another, rates estimated with pneumonia visits during the pandemic for children and adults were consistent in timing, peak, and magnitude., Conclusions: Estimated rates of influenza-associated outpatient visits were higher in children than adults during pre-pandemic and pandemic seasons. Rates estimated with pneumonia visits plus influenza-coded visits were similar to rates from studies using RT-PCR-confirmed influenza., (Published 2017. This article is a U.S. Government work and is in the public domain in the USA. Influenza and Other Respiratory Viruses published by John Wiley & Sons Ltd.)

Objective: Few studies have examined how acute respiratory illnesses (ARI) influence workplace productivity. We examined the association between laboratory-confirmed influenza and combined absenteeism/presenteeism., Methods: Linear regression was used to model the association between influenza (by seasonal vaccine status) and productivity loss over 7 to 17 days following symptom onset in 1278 employed adults in an influenza vaccine effectiveness study during the 2012 to 2013 through 2015 to 2016 seasons., Results: Influenza was significantly associated with workplace productivity loss (P < 0.001), but there were no significant differences between virus type/subtypes or seasonal vaccine status. Regardless of vaccination, participants with H1N1pdm09, H3N2, or B infection had the greatest mean productivity loss (range, 67% to 74%), while those with non-influenza ARI had the lowest productivity loss (58% to 59%)., Conclusions: Compared with non-influenza ARI, those with influenza lose an additional half day of work due to absenteeism/presenteeism over the week following symptom onset.

Background: Influenza-like illness and inflammation are known risk factors for venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE). However, few studies have characterized the risk of VTE following influenza vaccination. We examined VTE risk after vaccination in adults 50years old and older within the Vaccine Safety Datalink (VSD)., Methods: We used the self-controlled case series method to determine the risk of VTE among age-eligible adults who received influenza vaccine (with or without pandemic H1N1) and experienced a VTE during the months of September through December in 2007 through 2012. Presumptive VTE cases were identified among VSD participants using diagnostic codes, diagnostic tests, and oral anticoagulant prescription. Potential cases were validated by medical record review. The VTE incidence rate ratio was calculated among confirmed cases for the risk window 1 to 10days after vaccination relative to all other person-time from September through December., Results: Of the 1,488 presumptive cases identified, 508 were reviewed, of which 492 (97%) were confirmed cases of VTE. The analysis included 396 incident, confirmed cases. Overall, there was no increased risk of VTE in the 1 to 10days after influenza vaccination (IRR=0.89, 95% CI 0.69-1.17) compared to the control period. Results were similar when all person-time was censored before vaccination. A post hoc analysis showed an increased risk among current tobacco smokers (IRR=2.57, 95% CI 1.06-6.23). No clustering of VTE was observed in the 1-42days after vaccination., Discussion: Overall, there was no evidence that inactivated influenza vaccine was associated with VTE in adults ≥50years old. An increased risk was found among current smokers in a post hoc analysis. These findings are consistent with previous research and support the safety of annual vaccination in this population., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: Human papillomavirus (HPV) vaccine coverage rates remain low. This is believed to reflect parental hesitancy, but few studies have examined how changes in parents' attitudes impact HPV vaccine uptake. This study examined the association between changes in parents' vaccine attitudes and HPV vaccine receipt in their adolescent children., Methods: A baseline and 1-year follow-up survey of HPV vaccine attitudes was administered to parents of 11-17 year olds who had not completed the HPV vaccine series. Changes in attitudinal scores (barriers, harms, ineffectiveness, and uncertainties) from the Carolina HPV Immunization Attitudes and Beliefs Scale were assessed. Two outcomes were measured (in parents' adolescent children) over an 18-month period and analyzed using multivariable regression; receipt of next scheduled HPV vaccine dose and 3-dose series completion., Results: There were 221 parents who completed the baseline survey (11% response rate) and 164 with available follow-up data; 60% of their adolescent children received a next HPV vaccine dose and 38% completed the vaccine series at follow-up. Decrease in parents' uncertainties was a significant predictor of vaccine receipt, with each 1-point reduction in uncertainties score associated with 4.9 higher odds of receipt of the next vaccine dose. Higher baseline harms score was the only significant predictor of lower series completion., Conclusions: Reductions in parents' uncertainties appeared to result in greater likelihood of their children receiving the HPV vaccine. Only baseline concerns about vaccine harms were associated with lower series completion rate. Education for parents should emphasize the HPV vaccine's safety profile.

Introduction: Inactivated influenza vaccine is recommended in any stage of pregnancy, but evidence of safety in early pregnancy is limited, including for vaccines containing A/H1N1pdm2009 (pH1N1) antigen. We sought to determine if receipt of vaccine containing pH1N1 was associated with spontaneous abortion (SAB)., Methods: We conducted a case-control study over two influenza seasons (2010-11, 2011-12) in the Vaccine Safety Datalink. Cases had SAB and controls had live births or stillbirths and were matched on site, date of last menstrual period, and age. Of 919 potential cases identified using diagnosis codes, 485 were eligible and confirmed by medical record review. Exposure was defined as vaccination with inactivated influenza vaccine before the SAB date; the primary exposure window was the 1-28days before the SAB., Results: The overall adjusted odds ratio (aOR) was 2.0 (95% CI, 1.1-3.6) for vaccine receipt in the 28-day exposure window; there was no association in other exposure windows. In season-specific analyses, the aOR in the 1-28days was 3.7 (95% CI 1.4-9.4) in 2010-11 and 1.4 (95% CI 0.6-3.3) in 2011-12. The association was modified by influenza vaccination in the prior season (post hoc analysis). Among women who received pH1N1-containing vaccine in the previous influenza season, the aOR in the 1-28days was 7.7 (95% CI 2.2-27.3); the aOR was 1.3 (95% CI 0.7-2.7) among women not vaccinated in the previous season. This effect modification was observed in each season., Conclusion: SAB was associated with influenza vaccination in the preceding 28days. The association was significant only among women vaccinated in the previous influenza season with pH1N1-containing vaccine. This study does not and cannot establish a causal relationship between repeated influenza vaccination and SAB, but further research is warranted., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: The A(H1N1)pdm09 virus strain used in the live attenuated influenza vaccine was changed for the 2015-2016 influenza season because of its lack of effectiveness in young children in 2013-2014. The Influenza Vaccine Effectiveness Network evaluated the effect of this change as part of its estimates of influenza vaccine effectiveness in 2015-2016., Methods: We enrolled patients 6 months of age or older who presented with acute respiratory illness at ambulatory care clinics in geographically diverse U.S. sites. Using a test-negative design, we estimated vaccine effectiveness as (1-OR)×100, in which OR is the odds ratio for testing positive for influenza virus among vaccinated versus unvaccinated participants. Separate estimates were calculated for the inactivated vaccines and the live attenuated vaccine., Results: Among 6879 eligible participants, 1309 (19%) tested positive for influenza virus, predominantly for A(H1N1)pdm09 (11%) and influenza B (7%). The effectiveness of the influenza vaccine against any influenza illness was 48% (95% confidence interval [CI], 41 to 55; P<0.001). Among children 2 to 17 years of age, the inactivated influenza vaccine was 60% effective (95% CI, 47 to 70; P<0.001), and the live attenuated vaccine was not observed to be effective (vaccine effectiveness, 5%; 95% CI, -47 to 39; P=0.80). Vaccine effectiveness against A(H1N1)pdm09 among children was 63% (95% CI, 45 to 75; P<0.001) for the inactivated vaccine, as compared with -19% (95% CI, -113 to 33; P=0.55) for the live attenuated vaccine., Conclusions: Influenza vaccines reduced the risk of influenza illness in 2015-2016. However, the live attenuated vaccine was found to be ineffective among children in a year with substantial inactivated vaccine effectiveness. Because the 2016-2017 A(H1N1)pdm09 strain used in the live attenuated vaccine was unchanged from 2015-2016, the Advisory Committee on Immunization Practices made an interim recommendation not to use the live attenuated influenza vaccine for the 2016-2017 influenza season. (Funded by the Centers for Disease Control and Prevention and the National Institutes of Health.).

Purpose: Acceptance and coverage of the human papillomavirus (HPV) vaccine in the United States has been suboptimal. We implemented a multifaceted provider and staff intervention over a 1-year period to promote HPV vaccination in a regional health care system., Methods: The intervention was conducted in nine clinical departments from February 2015 to March 2016; 34 other departments served as controls. The intervention included in-person provider and staff education, quarterly feedback of vaccine coverage, and system-wide changes to patient reminder and recall notifications. Change in first-dose HPV vaccine coverage and series completion were estimated among 11- to 12-year-olds using generalized estimating equations adjusted for age and sex., Results: HPV vaccine coverage in the intervention departments increased from 41% to 59%, and the increase was significantly greater than that seen in the control departments (32%-45%, p = .0002). The largest increase occurred in the quarter after completion of the provider and staff education and a patient reminder and recall postcard mailing (p = .004). Series completion also increased significantly system wide among adolescents aged 11-12 years following mailing of HPV vaccine reminder letters to parents of adolescents aged 12 years rather than 16 years., Conclusions: HPV vaccine uptake can be improved through a multifaceted approach that includes provider and staff education and patient reminder/recall. System-level change to optimize reminder and recall notices can have substantial impact on HPV vaccine utilization., (Copyright © 2017 Society for Adolescent Health and Medicine. All rights reserved.)

Introduction: Studies in the 1970s and 1980s signaled concern that repeated influenza vaccination could affect vaccine protection. The antigenic distance hypothesis provided a theoretical framework to explain variability in repeat vaccination effects based on antigenic similarity between successive vaccine components and the epidemic strain. Areas covered: A meta-analysis of vaccine effectiveness studies from 2010-11 through 2014-15 shows substantial heterogeneity in repeat vaccination effects within and between seasons and subtypes. When negative effects were observed, they were most pronounced for H3N2, especially in 2014-15 when vaccine components were unchanged and antigenically distinct from the epidemic strain. Studies of repeated vaccination across multiple seasons suggest that vaccine effectiveness may be influenced by more than one prior season. In immunogenicity studies, repeated vaccination blunts the hemagglutinin antibody response, particularly for H3N2. Expert commentary: Substantial heterogeneity in repeated vaccination effects is not surprising given the variation in study populations and seasons, and the variable effects of antigenic distance and immunological landscape in different age groups and populations. Caution is required in the interpretation of pooled results across multiple seasons, since this can mask important variation in repeat vaccination effects between seasons. Multi-season clinical studies are needed to understand repeat vaccination effects and guide recommendations.

Background: A clinical study found that live attenuated influenza vaccine (LAIV) was superior to inactivated influenza vaccine (IIV) against drifted A(H3N2) viruses in children. During the 2014-2015 influenza season, widespread circulation of antigenically and genetically drifted A(H3N2) viruses provided an opportunity to evaluate subtype-specific vaccine effectiveness (VE) of quadrivalent LAIV (LAIV4) and IIV in children., Methods: Children (2-17years) with febrile acute respiratory illness <5days' duration were enrolled at 4 outpatient sites in the United States during the 2014-2015 influenza season. Nasal swabs were tested for influenza by reverse transcription polymerase chain reaction; vaccination dates were obtained from medical records or immunization registries. VE was estimated using a test-negative design comparing odds of vaccination among influenza cases and test-negative controls with adjustment for potential confounders., Results: Among 1696 children enrolled, 1511 (89%) were included in the analysis. Influenza was detected in 427 (28%) children; 317 had influenza A(H3N2) and 110 had influenza B. Most influenza isolates were characterized as a drifted strain of influenza A(H3N2) or a drifted strain of B/Yamagata. For LAIV4, adjusted VE was 50% (95% confidence interval [CI], 27-66%) against any influenza, 30% (95% CI, -6% to 54%) against influenza A(H3N2), and 87% (95% CI, 63-96%) against type B. For IIV, adjusted VE was 39% (95% CI, 18-54%) against any influenza, 40% (95% CI, 16-58%) against A(H3N2), and 29% (95% CI, -15% to 56%) against type B. Odds of influenza for LAIV4 versus IIV recipients were similar against influenza A(H3N2) (odds ratio [OR], 1.17; 95% CI, 0.73-1.86) and lower against influenza B (OR, 0.18; 95% CI, 0.06-0.55)., Conclusions: LAIV4 and IIV provided similar protection against a new antigenic variant A(H3N2). LAIV4 provided significantly greater protection than IIV against a drifted influenza B strain. ClinicalTrials.gov identifier: NCT01997450., (Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Acute respiratory illnesses (ARIs) are common in school-aged children, but few studies have assessed school absenteeism due to specific respiratory viruses., Objective: To evaluate school absenteeism among children with medically attended ARI due to common viruses., Methods: We analyzed follow-up surveys from children seeking care for acute respiratory illness who were enrolled in the influenza vaccine effectiveness study at Marshfield Clinic during the 2012-2013 through 2014-2015 influenza seasons. Archived influenza-negative respiratory swabs were retested using multiplex RT-PCR to detect 16 respiratory virus targets. Negative binomial and logistic regression models were used to examine the association between school absence and type of respiratory viruses; endpoints included mean days absent from school and prolonged (>2 days) absence. We examined the association between influenza vaccination and school absence among children with RT-PCR-confirmed influenza., Results: Among 1027 children, 2295 days of school were missed due to medically attended ARIs; influenza accounted for 39% of illness episodes and 47% of days missed. Mean days absent were highest for influenza (0.96-1.19) and lowest for coronavirus (0.62). Children with B/Yamagata infection were more likely to report prolonged absence than children with A/H1N1 or A/H3N2 infection [OR (95% CI): 2.1 (1.0, 4.5) and 1.7 (1.0, 2.9), respectively]. Among children with influenza, vaccination status was not associated with prolonged absence., Conclusions: School absenteeism due to medically attended ARIs varies by viral infection. Influenza B infections accounted for the greatest burden of absenteeism., (© 2016 The Authors. Influenza and Other Respiratory Viruses Published by John Wiley & Sons Ltd.)

Background: Live attenuated influenza vaccine (LAIV) might increase the risk of wheezing in persons with asthma or children younger than 5 years with a history of recurrent wheezing., Objective: To describe the use and assess the safety of LAIV in persons with asthma in the Vaccine Safety Datalink population., Methods: We identified persons with asthma using diagnosis codes and medication records in 7 health care organizations over 3 influenza seasons (2008-2009 through 2010-2011) and determined their influenza vaccination rates. Using the self-controlled risk interval method, we calculated the incidence rate ratio of medically attended respiratory events in the 14 days after LAIV compared with 29 to 42 days after vaccination in persons 2 through 49 years old., Results: In our population of 6.3 million, asthma prevalence was 5.9%. Of persons with asthma, approximately 50% received any influenza vaccine but less than 1% received LAIV. The safety study included 12,354 LAIV doses (75% in children; 93% in those with intermittent or mild persistent asthma). The incidence rate ratio for inpatient and emergency department visits for lower respiratory events (including asthma exacerbation and wheezing) was 0.98 (95% confidence interval 0.63-1.51) and the incidence rate ratio for upper respiratory events was 0.94 (95% confidence interval 0.48-1.86). The risk of lower respiratory events was similar for intermittent and mild persistent asthma, across age groups, and for seasonal trivalent LAIV and 2009 H1N1 pandemic monovalent LAIV., Conclusion: LAIV use in asthma was mostly in persons with intermittent or mild persistent asthma. LAIV was not associated with an increased risk of medically attended respiratory adverse events., (Published by Elsevier Inc.)

Background: Recent studies suggest that influenza vaccine effectiveness (VE) may wane over the course of an influenza season, leading to suboptimal VE during late influenza seasons., Methods: We examined the association between influenza VE and time since vaccination among patients ≥9 years old with medically-attended acute respiratory illness in the US Influenza Vaccine Effectiveness Network using data pooled from the 2011-12 through 2014-15 influenza seasons. We used multivariate logistic regression with PCR-confirmed influenza infection as the outcome and vaccination status defined by days between vaccination and symptom onset as the predictor. Models were adjusted for calendar time and other potential confounding factors., Results: We observed decreasing VE with increasing time since vaccination for influenza A(H3N2) (p=0.004), influenza A(H1N1)pdm09 (p=0.01), and influenza B viruses (p=0.04). Maximum VE was observed shortly after vaccination, followed by a decline in VE of about 7% (absolute) per month for influenza A(H3N2) and influenza B and 6% - 11% per month for influenza A(H1N1)pdm09 viruses. VE remained greater than zero for at least six months for influenza A(H1N1)pdm09 and influenza B and at least five months for influenza A(H3N2) viruses. Decline in VE was more pronounced among patients with prior season influenza vaccination. A similar pattern of increasing influenza risk with increasing time since vaccination was seen in analyses limited to vaccinees., Conclusions: We observed decreasing influenza vaccine protection with increasing time since vaccination across influenza types/subtypes. This association is consistent with intraseason waning of host immunity, but bias or residual confounding could explain these findings., (Published by Oxford University Press for the Infectious Diseases Society of America 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

In the United States, annual vaccination against seasonal influenza is recommended for all persons aged ≥6 months (1). Each influenza season since 2004-05, CDC has estimated the effectiveness of seasonal influenza vaccine to prevent influenza-associated, medically attended, acute respiratory illness (ARI). This report uses data, as of February 4, 2017, from 3,144 children and adults enrolled in the U.S. Influenza Vaccine Effectiveness Network (U.S. Flu VE Network) during November 28, 2016-February 4, 2017, to estimate an interim adjusted effectiveness of seasonal influenza vaccine for preventing laboratory-confirmed influenza virus infection associated with medically attended ARI. During this period, overall vaccine effectiveness (VE) (adjusted for study site, age group, sex, race/ethnicity, self-rated general health, and days from illness onset to enrollment) against influenza A and influenza B virus infection associated with medically attended ARI was 48% (95% confidence interval [CI] = 37%-57%). Most influenza infections were caused by A (H3N2) viruses. VE was estimated to be 43% (CI = 29%-54%) against illness caused by influenza A (H3N2) virus and 73% (CI = 54%-84%) against influenza B virus. These interim VE estimates indicate that influenza vaccination reduced the risk for outpatient medical visits by almost half. Because influenza activity remains elevated (2), CDC and the Advisory Committee on Immunization Practices recommend that annual influenza vaccination efforts continue as long as influenza viruses are circulating (1). Vaccination with 2016-17 influenza vaccines will reduce the number of infections with most currently circulating influenza viruses. Persons aged ≥6 months who have not yet been vaccinated this season should be vaccinated as soon as possible.

Background:  Circulating A/H3N2 influenza viruses drifted significantly after strain selection for the 2014-2015 vaccines. Also in 2014-2015, the Advisory Committee on Immunization Practices recommended preferential use of live attenuated influenza vaccine (LAIV) over inactivated influenza vaccine (IIV) among children aged 2-8 years., Methods:  Vaccine effectiveness (VE) across age groups and vaccine types was examined among outpatients with acute respiratory illness at 5 US sites using a test-negative design, that compared the odds of vaccination among reverse transcription polymerase chain reaction-confirmed influenza positives and negatives., Results:  Of 9311 enrollees with complete data, 7078 (76%) were influenza negative, 1840 (19.8%) were positive for influenza A (A/H3N2, n = 1817), and 395 (4.2%) were positive for influenza B (B/Yamagata, n = 340). The overall adjusted VE was 19% (95% confidence interval [CI], 10% to 27%) and was statistically significant in all age strata except those aged 18-64 years. The adjusted VE of 6% (95%CI, -5% to 17%) against A/H3N2-associated illness was not statistically significant, unlike VE for influenza B/Yamagata, which was 55% (95%CI, 43% to 65%). Among those aged 2-8 years, VE against A/H3N2 was 15% (95%CI, -16% to 38%) for IIV and -3% (CI, -50% to 29%) for LAIV; VE against B/Yamagata was 40% (95%CI, -20% to 70%) for IIV and 74% (95%CI, 25% to 91%) for LAIV., Conclusions:  The 2014-2015 influenza vaccines offered little protection against the predominant influenza A/H3N2 virus but were effective against influenza B. Preferential use of LAIV among young children was not supported., (Published by Oxford University Press for the Infectious Diseases Society of America 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

Background: Influenza viruses gradually accumulate point mutations, reducing the effectiveness of prior immune protection., Methods: Children aged 9-14 years received 2010-2011 trivalent inactivated influenza vaccine (TIV). Vaccination history, hemagglutination-inhibition (HI) titers, and cell-mediated immune responses were assessed to investigate the cross-reactivity with past and future influenza virus strains., Results: 2010-2011 TIV induced significant T-cell responses and HI titers of ≥160, with a fold-rise of ≥4 and titers of ≥100 maintained for >7 months in the majority of children. Pre-existing memory B cells in these children differentiated quickly to antibody-secreting cells to the new vaccine antigens. Children vaccinated in the previous year maintained high HI titers well into 2010, demonstrating elevated HI titers against A/Perth/16/2009, the future (in 2010-2011) H3N2 component. Prior vaccination enhanced CD8 + T-cell responses to A/Perth/16/2009. Children vaccinated with the prior 2009-2010 seasonal vaccine also demonstrated higher preexisting levels of interferon γ-secreting CD4 + CD69 + T cells to 2009 pandemic influenza A(H1N1). Children previously vaccinated with 2009-2010 seasonal influenza vaccine also showed greater expansion of tumor necrosis factor α-secreting CD8 + CD69 + T cells to 2009 pandemic influenza A(H1N1) upon vaccination in the 2010-2011 season than those who were not previously vaccinated., Conclusions: Seasonal influenza viruses continuously drift, which allows them to circumvent protective immunity, but conserved epitopes provide immunological cross-reactivity in children through either vaccination directly or through prime/boost in the prior influenza season., (Published by Oxford University Press for the Infectious Diseases Society of America 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

Background: Recent studies suggest that statin use may reduce influenza vaccine effectiveness (VE), but laboratory-confirmed influenza was not assessed., Methods: Patients ≥45 years old presenting with acute respiratory illness were prospectively enrolled during the 2004-2005 through 2014-2015 influenza seasons. Vaccination and statin use were extracted from electronic records. Respiratory samples were tested for influenza virus., Results: The analysis included 3285 adults: 1217 statin nonusers (37%), 903 unvaccinated statin nonusers (27%), 847 vaccinated statin users (26%), and 318 unvaccinated statin users (10%). Statin use modified VE and the risk of influenza A(H3N2) virus infection (P = .002) but not 2009 pandemic influenza A(H1N1) virus (A[H1N1]pdm09) or influenza B virus infection (P = .2 and .4, respectively). VE against influenza A(H3N2) was 45% (95% confidence interval [CI], 27%-59%) among statin nonusers and -21% (95% CI, -84% to 20%) among statin users. Vaccinated statin users had significant protection against influenza A(H1N1)pdm09 (VE, 68%; 95% CI, 19%-87%) and influenza B (VE, 48%; 95% CI, 1%-73%). Statin use did not significantly modify VE when stratified by prior season vaccination. In validation analyses, the use of other cardiovascular medications did not modify influenza VE., Conclusions: Statin use was associated with reduced VE against influenza A(H3N2) but not influenza A(H1N1)pdm09 or influenza B. Further research is needed to assess biologic plausibility and confirm these results., (© The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America.)

Background: During the 2014-2015 US influenza season, expanded genetic characterization of circulating influenza A(H3N2) viruses was used to assess the impact of the genetic variability of influenza A(H3N2) viruses on influenza vaccine effectiveness (VE)., Methods: A novel pyrosequencing assay was used to determine genetic group, based on hemagglutinin (HA) gene sequences, of influenza A(H3N2) viruses from patients enrolled at US Influenza Vaccine Effectiveness Network sites. VE was estimated using a test-negative design comparing vaccination among patients infected with influenza A(H3N2) viruses and uninfected patients., Results: Among 9710 enrollees, 1868 (19%) tested positive for influenza A(H3N2) virus; genetic characterization of 1397 viruses showed that 1134 (81%) belonged to 1 HA genetic group (3C.2a) of antigenically drifted influenza A(H3N2) viruses. Effectiveness of 2014-2015 influenza vaccination varied by influenza A(H3N2) virus genetic group from 1% (95% confidence interval [CI], -14% to 14%) against illness caused by antigenically drifted influenza A(H3N2) virus group 3C.2a viruses versus 44% (95% CI, 16%-63%) against illness caused by vaccine-like influenza A(H3N2) virus group 3C.3b viruses., Conclusions: Effectiveness of 2014-2015 influenza vaccination varied by genetic group of influenza A(H3N2) virus. Changes in HA genes related to antigenic drift were associated with reduced VE., (Published by Oxford University Press for the Infectious Diseases Society of America 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

Background: The use of neuraminidase-inhibiting anti-viral medication to treat influenza is relatively infrequent. Rapid, cost-effective methods for diagnosing influenza are needed to enable appropriate prescribing. Multi-viral respiratory panels using reverse transcription polymerase chain reaction (PCR) assays to diagnose influenza are accurate but expensive and more time-consuming than low sensitivity rapid influenza tests. Influenza clinical decision algorithms are both rapid and inexpensive, but most are based on regression analyses that do not account for higher order interactions. This study used classification and regression trees (CART) modeling to estimate probabilities of influenza., Methods: Eligible enrollees ≥ 5 years old (n = 4,173) who presented at ambulatory centers for treatment of acute respiratory illness (≤7 days) with cough or fever in 2011-2012, provided nasal and pharyngeal swabs for PCR testing for influenza, information on demographics, symptoms, personal characteristics and self-reported influenza vaccination status., Results: Antiviral medication was prescribed for just 15 % of those with PCR-confirmed influenza. An algorithm that included fever, cough, and fatigue had sensitivity of 84 %, specificity of 48 %, positive predictive value (PPV) of 23 % and negative predictive value (NPV) of 94 % for the development sample., Conclusions: The CART algorithm has good sensitivity and high NPV, but low PPV for identifying influenza among outpatients ≥5 years. Thus, it is good at identifying a group who do not need testing or antivirals and had fair to good predictive performance for influenza. Further testing of the algorithm in other influenza seasons would help to optimize decisions for lab testing or treatment.

Purpose: The changes in each year in influenza vaccine antigenic components as well as vaccine administration patterns may pose new risks of adverse events following immunization (AEs). To evaluate the safety of influenza vaccines annually administered to people ≥ 6 months, we conducted weekly post licensure surveillance for seven pre-specified adverse events following receipt of influenza vaccines during the 2013-2014 and 2014-2015 seasons in the Vaccine Safety Datalink (VSD)., Methods: We used both a historically-controlled cohort design with the Poisson-based maximized sequential probability ratio test (maxSPRT) and a self-controlled risk interval (SCRI) design with the binomial-based maxSPRT. For each adverse event outcome, we defined the risk interval on the basis of biologic plausibility and prior literature. For the historical cohort design, numbers of expected adverse events were calculated from the prior seven seasons, adjusted for age and site. For the SCRI design, a comparison window was defined either before vaccination or after vaccination, depending on each specific outcome., Results: An elevated risk of febrile seizures 0-1 days following trivalent inactivated influenza vaccine (IIV3) was identified in children aged 6-23 months during the 2014-2015 season using the SCRI design. We found the relative risk (RR) of febrile seizures following concomitant administration of IIV3 and PCV13 was 5.3 with a 95% CI 1.87-14.75. Without concomitant PCV 13 administration, the estimated risk decreased and was no longer statistically significant (RR: 1.4; CI: 0.54 - 3.61)., Conclusion: No increased risks, other than for febrile seizures, were identified in influenza vaccine safety surveillance during 2013-2014 and 2014-2015 seasons in the VSD. Copyright © 2016 John Wiley & Sons, Ltd., (Copyright © 2016 John Wiley & Sons, Ltd.)

Background: Influenza vaccine effectiveness (VE) can vary by type and subtype. Over the past decade, the test-negative design has emerged as a valid method for estimation of VE. In this design, VE is calculated as 100% × (1 - odds ratio) for vaccine receipt in influenza cases versus test-negative controls. We did a systematic review and meta-analysis to estimate VE by type and subtype., Methods: In this systematic review and meta-analysis, we searched PubMed and Embase from Jan 1, 2004, to March 31, 2015. Test-negative design studies of influenza VE were eligible if they enrolled outpatients on the basis of predefined illness criteria, reported subtype-level VE by season, used PCR to confirm influenza, and adjusted for age. We excluded studies restricted to hospitalised patients or special populations, duplicate reports, interim reports superseded by a final report, studies of live-attenuated vaccine, and studies of prepandemic seasonal vaccine against H1N1pdm09. Two reviewers independently assessed titles and abstracts to identify articles for full review. Discrepancies in inclusion and exclusion criteria and VE estimates were adjudicated by consensus. Outcomes were VE against H3N2, H1N1pdm09, H1N1 (pre-2009), and type B. We calculated pooled VE using a random-effects model., Findings: We identified 3368 unduplicated publications, selected 142 for full review, and included 56 in the meta-analysis. Pooled VE was 33% (95% CI 26-39; I(2)=44·4) for H3N2, 54% (46-61; I(2)=61·3) for type B, 61% (57-65; I(2)=0·0) for H1N1pdm09, and 67% (29-85; I(2)=57·6) for H1N1; VE was 73% (61-81; I(2)=31·4) for monovalent vaccine against H1N1pdm09. VE against H3N2 for antigenically matched viruses was 33% (22-43; I(2)=56·1) and for variant viruses was 23% (2-40; I(2)=55·6). Among older adults (aged >60 years), pooled VE was 24% (-6 to 45; I(2)=17·6) for H3N2, 63% (33-79; I(2)=0·0) for type B, and 62% (36-78; I(2)=0·0) for H1N1pdm09., Interpretation: Influenza vaccines provided substantial protection against H1N1pdm09, H1N1 (pre-2009), and type B, and reduced protection against H3N2. Vaccine improvements are needed to generate greater protection against H3N2 than with current vaccines., Funding: None., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The relationship between age, vitamin D status, expression and functionality of the vitamin D receptor (VDR), and key genes in the vitamin D pathway in immune cells is unclear. We enrolled adults 50 to 69 years old (20 subjects) and 70+ (20 subjects) and measured: 1) 25(OH)D levels by liquid chromatography/mass spectrometry; and 2) mRNA expression of VDR, 1α-OHase, 1,25D3-MARRS, TREM-1, cathelicidin, RIG-I, and interferon-β by qRT-PCR. Mean serum 25(OH)D was 30 ± 4 ng/mL and was not associated with age. Baseline expression of VDR, 1α-OHase, 1,25D3-MARRS, TREM-1, and RIG-I also did not differ by age; IFN-β expression, however, was higher in the 70+ year old group. 25(OH)D3- and 1,25(OH)2D3-induced VDR, TREM-1 and cathelicidin expression were similar between age groups, as was LPS-induced expression of VDR and of 1α-OHase. Ligand-induced 1,25D3-MARRS expression was higher in subjects ≥ 70 years. Serum 25(OH)D was inversely associated with LPS-stimulated VDR expression and with baseline or vitamin D-induced TREM-1 expression, adjusting for age, self-rated health, and functional status. In healthy adults ≥ 50 years, the expression and functionality of the VDR, 1α-OHase and key vitamin D pathway genes were not consistently associated with age., Competing Interests: The authors, MM, MT, SMS, AJR, WGD, P-YC, EAB, DKS and SS declare no conflict of interest. HKT has received research funding from Sanofi Pasteur, MedImmune, and Gilead; and she serves on Advisory Boards for Teva Pharmaceuticals and MedImmune. MES has received research funding from MedImmune. MRG receives research funding from MedImmune. LAC is an employee of Abbott Nutrition.

Background: The predominant strain during the 2013-2014 influenza season was 2009 pandemic influenza A(H1N1) virus (A[H1N1]pdm09). This vaccine-component has remained unchanged from 2009., Methods: The US Flu Vaccine Effectiveness Network enrolled subjects aged ≥6 months with medically attended acute respiratory illness (MAARI), including cough, with illness onset ≤7 days before enrollment. Influenza was confirmed by reverse-transcription polymerase chain reaction (RT-PCR). We determined the effectiveness of trivalent or quadrivalent inactivated influenza vaccine (IIV) among subjects ages ≥6 months and the effectiveness of quadrivalent live attenuated influenza vaccine (LAIV4) among children aged 2-17 years, using a test-negative design. The effect of prior receipt of any A(H1N1)pdm09-containing vaccine since 2009 on the effectiveness of current-season vaccine was assessed., Results: We enrolled 5999 subjects; 5637 (94%) were analyzed; 18% had RT-PCR-confirmed A(H1N1)pdm09-related MAARI. Overall, the effectiveness of vaccine against A(H1N1)pdm09-related MAARI was 54% (95% confidence interval [CI], 46%-61%). Among fully vaccinated children aged 2-17 years, the effectiveness of LAIV4 was 17% (95% CI, -39% to 51%) and the effectiveness of IIV was 60% (95% CI, 36%-74%). Subjects aged ≥9 years showed significant residual protection of any prior A(H1N1)pdm09-containing vaccine dose(s) received since 2009, as did children <9 years old considered fully vaccinated by prior season., Conclusions: During 2013-2014, IIV was significantly effective against A(H1N1)pdm09. Lack of LAIV4 effectiveness in children highlights the importance of continued annual monitoring of effectiveness of influenza vaccines in the United States., (© The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail journals.permissions@oup.com.)

Background.  Respiratory syncytial virus (RSV) and influenza are significant causes of seasonal respiratory illness in children. The incidence of influenza and RSV hospitalization is well documented, but the incidence of medically attended, laboratory-confirmed illness has not been assessed in a well defined community cohort. Methods.  Children aged 6-59 months with medically attended acute respiratory illness were prospectively enrolled during the 2006-2007 through 2009-2010 influenza seasons in a Wisconsin community cohort. Nasal swabs were tested for RSV and influenza by multiplex reverse-transcription polymerase chain reaction. The population incidence of medically attended RSV and influenza was estimated separately and standardized to weeks 40 through 18 of each season. Results.  The cohort included 2800-3073 children each season. There were 2384 children enrolled with acute respiratory illness; 627 (26%) were positive for RSV and 314 (13%) for influenza. The mean age was 28 months (standard deviation [SD] = 15) for RSV-positive and 38 months (SD = 16) for influenza-positive children. Seasonal incidence (cases per 10 000) was 1718 (95% confidence interval [CI], 1602-1843) for RSV and 768 (95% CI, 696-848) for influenza. Respiratory syncytial virus incidence was highest among children 6-11 (2927) and 12-23 months old (2377). Influenza incidence was highest (850) in children 24-59 months old. The incidence of RSV was higher than influenza across all seasons and age groups. Conclusions.  The incidence of medically attended RSV was highest in children 6-23 months old, and it was consistently higher than influenza. The burden of RSV remains high throughout the first 2 years of life.

Background: Two doses of measles, mumps, and rubella (MMR) vaccine are 97% effective against measles, but waning antibody immunity to measles and failure of the 2-dose vaccine occur. We administered a third MMR dose (MMR3) to young adults and assessed immunogenicity over 1 year., Methods: Measles virus (MeV) neutralizing antibody concentrations, cell-mediated immunity (CMI), and immunoglobulin G (IgG) antibody avidity were assessed at baseline and 1 month and 1 year after MMR3 receipt., Results: Of 662 subjects at baseline, 1 (0.2%) was seronegative for MeV-neutralizing antibodies (level, <8 mIU/mL), and 23 (3.5%) had low antibody levels (8-120 mIU/mL). One month after MMR3 receipt, 1 subject (0.2%) was seronegative, and 6 (0.9%) had low neutralizing antibodies, with only 21 of 662 (3.2%) showing a ≥ 4-fold rise in neutralizing antibodies. One year after MMR3 receipt, no subject was seronegative, and 10 of 617 (1.6%) had low neutralizing antibody levels. CMI analyses showed low levels of spot-forming cells after stimulation, suggesting the presence of T-cell memory, but the response was minimal after MMR3 receipt. MeV IgG avidity did not correlate with findings of neutralization analyses., Conclusions: Most subjects were seropositive before MMR3 receipt, and very few had a secondary immune response after MMR3 receipt. Similarly, CMI and avidity analyses showed minimal qualitative improvements in immune response after MMR3 receipt. We did not find compelling data to support a routine third dose of MMR vaccine., (Published by Oxford University Press for the Infectious Diseases Society of America 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

We evaluated the cycle threshold (CT) values of 1,160 influenza A positive and 806 influenza B positive specimens from two seasons of the US Flu VE Network to identify factors associated with CT values. Low CT values (high genomic load) were associated with shorter intervals between illness onset and specimen collection, young age (ages 3-8 years old), and self-rated illness severity for both influenza A and B. Low CT values were also associated with reported fever/feverishness and age ≥65 years for influenza A., (© 2015 Wiley Periodicals, Inc.)

Background: Few studies have examined the effectiveness of full versus partial vaccination with inactivated trivalent influenza vaccines (IIV3) as defined by the US CDC Advisory Committee on Immunization Practices., Methods: Respiratory swabs were collected from outpatients aged 6 months to 8 years with acute cough for ≤7 days in clinics in 5 states during the 2011-2012 and 2012-2013 influenza seasons. Influenza was confirmed by real-time reverse transcription polymerase chain reaction assay. Receipt of current season IIV3 and up to 4 prior vaccinations was documented from medical records and immunization registries. Using a test-negative design, vaccine effectiveness (VE) was estimated adjusting for age, race/ethnicity, medical conditions, study site and month of enrollment., Results: We did not observe higher VE for children fully versus partially vaccinated with IIV3, as defined by US Advisory Committee on Immunization Practice, although our sample of partially vaccinated children was relatively small. However, among children aged 2-8 years in both seasons and against A(H3N2) and B influenza illness separately, VE point estimates were consistently higher for children who had received 2 doses in the same prior season compared with those without (VE range of 58%-80% vs. 33%-44%, respectively). Across seasons, the odds of A(H3N2) illness despite IIV3 vaccination were 2.4-fold (95% confidence interval: 1.4-4.3) higher among children who had not received 2 doses in the same prior season. We also noted residual protection among unvaccinated children who were vaccinated the previous season (VE range = 36%-40% across outcomes)., Conclusion: Vaccination with IIV3 may provide preventive benefit in subsequent seasons, including possible residual protection if vaccination is missed. Two vaccine doses in the same season may be more effective than alternative priming strategies.

Background: Few observational studies have evaluated the relative effectiveness of live attenuated (LAIV) and inactivated (IIV) influenza vaccines against medically attended laboratory-confirmed influenza., Methods: We analyzed US Influenza Vaccine Effectiveness Network data from participants aged 2 to 17 years during 4 seasons (2010-2011 through 2013-2014) to compare relative effectiveness of LAIV and IIV against influenza-associated illness. Vaccine receipt was confirmed via provider/electronic medical records or immunization registry. We calculated the ratio (odds) of influenza-positive to influenza-negative participants among those age-appropriately vaccinated with either LAIV or IIV for the corresponding season. We examined relative effectiveness of LAIV and IIV by using adjusted odds ratios (ORs) and 95% confidence intervals (CIs) from logistic regression., Results: Of 6819 participants aged 2 to 17 years, 2703 were age-appropriately vaccinated with LAIV (n = 637) or IIV (n = 2066). Odds of influenza were similar for LAIV and IIV recipients during 3 seasons (2010-2011 through 2012-2013). In 2013-2014, odds of influenza were significantly higher among LAIV recipients compared with IIV recipients 2 to 8 years old (OR 5.36; 95% CI, 2.37 to 12.13). Participants vaccinated with LAIV or IIV had similar odds of illness associated with influenza A/H3N2 or B. LAIV recipients had greater odds of illness due to influenza A/H1N1pdm09 in 2010-2011 and 2013-2014., Conclusions: We observed lower effectiveness of LAIV compared with IIV against influenza A/H1N1pdm09 but not A(H3N2) or B among children and adolescents, suggesting poor performance related to the LAIV A/H1N1pdm09 viral construct., (Copyright © 2016 by the American Academy of Pediatrics.)

Unlabelled: Influenza vaccines must be frequently reformulated to account for antigenic changes in the viral envelope protein, hemagglutinin (HA). The rapid evolution of influenza virus under immune pressure is likely enhanced by the virus's genetic diversity within a host, although antigenic change has rarely been investigated on the level of individual infected humans. We used deep sequencing to characterize the between- and within-host genetic diversity of influenza viruses in a cohort of patients that included individuals who were vaccinated and then infected in the same season. We characterized influenza HA segments from the predominant circulating influenza A subtypes during the 2012-2013 (H3N2) and 2013-2014 (pandemic H1N1; H1N1pdm) flu seasons. We found that HA consensus sequences were similar in nonvaccinated and vaccinated subjects. In both groups, purifying selection was the dominant force shaping HA genetic diversity. Interestingly, viruses from multiple individuals harbored low-frequency mutations encoding amino acid substitutions in HA antigenic sites at or near the receptor-binding domain. These mutations included two substitutions in H1N1pdm viruses, G158K and N159K, which were recently found to confer escape from virus-specific antibodies. These findings raise the possibility that influenza antigenic diversity can be generated within individual human hosts but may not become fixed in the viral population even when they would be expected to have a strong fitness advantage. Understanding constraints on influenza antigenic evolution within individual hosts may elucidate potential future pathways of antigenic evolution at the population level., Importance: Influenza vaccines must be frequently reformulated due to the virus's rapid evolution rate. We know that influenza viruses exist within each infected host as a "swarm" of genetically distinct viruses, but the role of this within-host diversity in the antigenic evolution of influenza has been unclear. We characterized here the genetic and potential antigenic diversity of influenza viruses infecting humans, some of whom became infected despite recent vaccination. Influenza virus between- and within-host genetic diversity was not significantly different in nonvaccinated and vaccinated humans, suggesting that vaccine-induced immunity does not exert strong selective pressure on viruses replicating in individual people. We found low-frequency mutations, below the detection threshold of traditional surveillance methods, in nonvaccinated and vaccinated humans that were recently associated with antibody escape. Interestingly, these potential antigenic variants did not reach fixation in infected people, suggesting that other evolutionary factors may be hindering their emergence in individual humans., (Copyright © 2016, American Society for Microbiology. All Rights Reserved.)

Background: A postmarketing observational study was initiated to evaluate quadrivalent live attenuated influenza vaccine (LAIV) effectiveness in children aged 2-17 years in the United States., Methods: Children and adolescents aged 2-17 years seeking outpatient care for febrile acute respiratory illness <5 days duration were enrolled at 4 geographically diverse sites during the 2013-2014 influenza season. Nasal swabs were tested for influenza using reverse transcription polymerase chain reaction. Vaccination status was documented from medical records or immunization registries. Children who received ≥1 dose of influenza vaccine ≥14 days before study visit were considered vaccinated. Vaccine effectiveness (VE) was estimated as 100×(1-adjusted odds ratio), where the odds of interest are the odds of vaccine exposure among influenza cases and test-negative controls., Results: In total, 1033 children and adolescents were included in the analysis. Influenza was detected in 14% (145/1033) of all children, with 74% (108/145) of the influenza cases due to A/H1N1pdm09 strains, 21% (31) to influenza B, and 4% (6) to influenza H3N2. LAIV did not show significant effectiveness against A/H1N1pdm09 (VE 13% [95% CI: -55 to 51]) but was effective against B/Yamagata strains (82% [95% CI: 12-96]). Inactivated influenza vaccine was effective against A/H1N1pdm09 (74% [95% CI: 50-86]) and B/Yamagata (70% [95% CI: 18-89])., Conclusions: LAIV provided significant protection against B/Yamagata influenza but not against A/H1N1pdm09 in children aged 2-17 years in 2013-2014, resulting in a proposed change of the 2015-2016 formulation with a new and more heat-stable A/H1N1pdm09 LAIV strain., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Objective: In this study, health event capture is broadly defined as the degree to which a group of people use a particular provider network as their primary source of health care services. The Marshfield Epidemiologic Study Area (MESA) is a valuable resource for population-based health research, but the completeness of health event capture has not been validated in recent years. Our objective was to determine the current level of outpatient and inpatient health event capture by Marshfield Clinic (MC) facilities and affiliated hospitals for people living within MESA., Design: A stratified sample survey with strata defined by MESA region (Central or North) and age group (<18 years or ≥18 years)., Setting: 24 ZIP codes in central and northern Wisconsin, USA., Participants: 2,485 individuals participated of the 4,313 sampled cohort members residing in MESA Central (N=61,041) and MESA North (N=25,906) on February 22, 2011., Methods: A health care utilization survey was mailed to a random sample stratified by age group and MESA region. Telephone interviews were attempted for nonrespondents. The survey requested information on sources of outpatient care and overnight hospital admissions. Population proportions representing health event capture metrics and corresponding 95% confidence intervals (CI) were estimated with analytic weights applied to account for the survey design., Results: Among those with an outpatient visit during the past 24 months, the most recent visit of an estimated 93% (95% CI, 91% - 94%) was at a MC facility. The most recent admission of an estimated 93% (95% CI, 90% - 96%) of those hospitalized in the past 24 months was at a hospital affiliated with MC. The proportion admitted to MC affiliated hospitals was higher for residents of MESA Central (97%) compared to MESA North (83%)., Conclusion: A high proportion of outpatient visits and inpatient admissions in MESA Central and MESA North are accessible in the MC electronic health record. This pattern of high health event capture has been demonstrated since the inception of MESA in 1991. The results from this study validate and support the continued use of MESA for population-based epidemiologic and clinical research., (© 2015 Marshfield Clinic.)

We used the winter of 2009-2010, which had minimal influenza circulation due to the earlier 2009 influenza A(H1N1) pandemic, to test the accuracy of ecological trend methods used to estimate influenza-related deaths and hospitalizations. We aggregated weekly counts of person-time, all-cause deaths, and hospitalizations for pneumonia/influenza and respiratory/circulatory conditions from seven healthcare systems. We predicted the incidence of the outcomes during the winter of 2009-2010 using three different methods: a cyclic (Serfling) regression model, a cyclic regression model with viral circulation data (virological regression), and an autoregressive, integrated moving average model with viral circulation data (ARIMAX). We compared predicted non-influenza incidence with actual winter incidence. All three models generally displayed high accuracy, with prediction errors for death ranging from -5% to -2%. For hospitalizations, errors ranged from -10% to -2% for pneumonia/influenza and from -3% to 0% for respiratory/circulatory. The Serfling and virological models consistently outperformed the ARIMAX model. The three methods tested could predict incidence of non-influenza deaths and hospitalizations during a winter with negligible influenza circulation. However, meaningful mis-estimation of the burden of influenza can still result with outcomes for which the contribution of influenza is low, such as all-cause mortality.

We conducted a double-blind, randomized trial of 134 outpatients with polymerase chain reaction-confirmed influenza to assess the effects of oseltamivir initiated 48-119 hours after illness onset. Oseltamivir treatment did not reduce illness duration, severity, or duration of virus detection. However, the power of this study was limited due to lower than expected enrollment.

During the 2013-2014 influenza season, we analyzed data from 6004 outpatients aged ≥6 months with acute respiratory illness (ARI). Among the 2786 ARI patients at higher risk for influenza complications, 835 (30%) presented to care ≤2 days from symptom onset; among those, 126 (15%) were prescribed an antiviral medication., (Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

Background: During the 2012-2013 influenza season, there was cocirculation of influenza A(H3N2) and 2 influenza B lineage viruses in the United States., Methods: Patients with acute cough illness for ≤7 days were prospectively enrolled and had swab samples obtained at outpatient clinics in 5 states. Influenza vaccination dates were confirmed by medical records. The vaccine effectiveness (VE) was estimated as [100% × (1 - adjusted odds ratio)] for vaccination in cases versus test-negative controls., Results: Influenza was detected in 2307 of 6452 patients (36%); 1292 (56%) had influenza A(H3N2), 582 (25%) had influenza B/Yamagata, and 303 (13%) had influenza B/Victoria. VE was 49% (95% confidence interval [CI], 43%-55%) overall, 39% (95% CI, 29%-47%) against influenza A(H3N2), 66% (95% CI, 58%-73%) against influenza B/Yamagata (vaccine lineage), and 51% (95% CI, 36%-63%) against influenza B/Victoria. VE against influenza A(H3N2) was highest among persons aged 50-64 years (52%; 95% CI, 33%-65%) and persons aged 6 months-8 years (51%; 95% CI, 32%-64%) and lowest among persons aged ≥65 years (11%; 95% CI, -41% to 43%). In younger age groups, there was evidence of residual protection from receipt of the 2011-2012 vaccine 1 year earlier., Conclusions: The 2012-2013 vaccines were moderately effective in most age groups. Cross-lineage protection and residual effects from prior vaccination were observed and warrant further investigation., (© The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America.)

Background: Little is known about factors associated with maintenance of hemagglutinin inhibition (HAI) antibodies after influenza vaccination in older adults., Methods: Adults ≥50 years of age were vaccinated prior to the 2009-10 influenza season. Serum was drawn pre-vaccination (S1), 21-28 days post-vaccination (S2), and after the influenza season (S3) for HAI assays. Seroconversion was defined as ≥ 4-fold increase S1 to S2 (or if S1 < 10, by an S2 ≥ 40) and seroprotection was defined as S2 ≥ 40. Maintenance of antibody response was measured in participants with an S2 ≥ 40, and defined as an S3 ≥ 40., Results: We enrolled 510 participants during Fall 2009 at Vanderbilt University Medical Center and Marshfield Clinic Research Foundation. Participants' mean age was 64 years with 62% female and 96% white. Seroconversion and seroprotection rates were lowest for influenza A H1N1 (12% and 26%, respectively), highest for influenza A H3N2 (45% and 82%), and intermediate for influenza B (28% and 72%). Of the participants with an S2 ≥ 40, 36% (46/126), 71% (289/407), and 74% (263/354) maintained an S3 ≥ 40 for H1N1, H3N2, and B influenza vaccine strains, respectively. S1 HAI titer was strongly associated with both post-vaccination seroprotection and maintaining seroprotection at S3 for all three influenza antigens. Age, sex, body mass index, self-reported stress, and vaccination site were not consistently associated with vaccine response or maintenance of response., Conclusions: Pre-vaccination antibody titer was the only study variable consistently and positively associated with both serologic response to vaccination and maintenance of response. Antibody responses were lowest for the H1N1 vaccine strain., Clinicaltrials: gov Identifier: NCT02401893.

Background.  Influenza disproportionately impacts older adults while current vaccines have reduced effectiveness in the older population. Methods.  We conducted a comprehensive evaluation of cellular and humoral immune responses of adults aged 50 years and older to the 2008-2009 seasonal trivalent inactivated influenza vaccine and assessed factors influencing vaccine response. Results.  Vaccination increased hemagglutination inhibition and neutralizing antibody; however, 66.3% of subjects did not reach hemagglutination inhibition titers ≥ 40 for H1N1, compared with 22.5% for H3N2. Increasing age had a minor negative impact on antibody responses, whereas prevaccination titers were the best predictors of postvaccination antibody levels. Preexisting memory B cells declined with age, especially for H3N2. However, older adults still demonstrated a significant increase in antigen-specific IgG(+) and IgA(+) memory B cells postvaccination. Despite reduced frequency of preexisting memory B cells associated with advanced age, fold-rise in memory B cell frequency in subjects 60+ was comparable to subjects age 50-59. Conclusions.  Older adults mounted statistically significant humoral and cell-mediated immune responses, but many failed to reach hemagglutination inhibition titers ≥40, especially for H1N1. Although age had a modest negative effect on vaccine responses, prevaccination titers were the best predictor of postvaccination antibody levels, irrespective of age.

Background and Objectives: All measles-containing vaccines are associated with several types of adverse events, including seizure, fever, and immune thrombocytopenia purpura (ITP). Because the measles-mumps-rubella-varicella (MMRV) vaccine compared with the separate measles-mumps-rubella (MMR) and varicella (MMR + V) vaccine increases a toddler's risk for febrile seizures, we investigated whether MMRV is riskier than MMR + V and whether either vaccine elevates the risk for additional safety outcomes., Methods: Study children were aged 12 to 23 months in the Vaccine Safety Datalink from 2000 to 2012. Nine study outcomes were investigated: 7 main outcomes (anaphylaxis, ITP, ataxia, arthritis, meningitis/encephalitis, acute disseminated encephalomyelitis, and Kawasaki disease), seizure, and fever. Comparing MMRV with MMR + V, relative risk was estimated by using stratified exact binomial tests. Secondary analyses examined post-MMRV or MMR + V risk versus comparison intervals; risk and comparison intervals were then contrasted for MMRV versus MMR+V., Results: We evaluated 123,200 MMRV and 584,987 MMR + V doses. Comparing MMRV with MMR + V, risks for the 7 main outcomes were not significantly different. Several outcomes had few or zero postvaccination events. Comparing risk versus comparison intervals, ITP risk was higher after MMRV (odds ratio [OR]: 11.3 [95% confidence interval (CI): 1.9 to 68.2]) and MMR + V (OR: 10 [95% CI: 4.5 to 22.5]) and ataxia risk was lower after both vaccines (MMRV OR: 0.8 [95% CI: 0.5 to 1]; MMR + V OR: 0.8 [95% CI: 0.7 to 0.9]). Compared with MMR + V, MMRV increased risk of seizure and fever 7 to 10 days after vaccination., Conclusions: This study did not identify any new safety concerns comparing MMRV with MMR + V or after either the MMRV or the MMR + V vaccine. This study provides reassurance that these outcomes are unlikely after either vaccine., (Copyright © 2015 by the American Academy of Pediatrics.)

In the United States, annual vaccination against seasonal influenza is recommended for all persons aged ≥6 months. Each season since 2004-05, CDC has estimated the effectiveness of seasonal influenza vaccine in preventing medically attended acute respiratory illness (ARI) associated with laboratory-confirmed influenza. This season, early estimates of influenza vaccine effectiveness are possible because of widespread, early circulation of influenza viruses. By January 3, 2015, 46 states were experiencing widespread flu activity, with predominance of influenza A (H3N2) viruses. This report presents an initial estimate of seasonal influenza vaccine effectiveness at preventing laboratory-confirmed influenza virus infection associated with medically attended ARI based on data from 2,321 children and adults enrolled in the U.S. Influenza Vaccine Effectiveness Network (Flu VE) during November 10, 2014-January 2, 2015. During this period, overall vaccine effectiveness (VE) (adjusted for study site, age, sex, race/ethnicity, self-rated health, and days from illness onset to enrollment) against laboratory-confirmed influenza associated with medically attended ARI was 23% (95% confidence interval [CI] = 8%-36%). Most influenza infections were due to A (H3N2) viruses. This interim VE estimate is relatively low compared with previous seasons when circulating viruses and vaccine viruses were well-matched and likely reflects the fact that more than two-thirds of circulating A (H3N2) viruses are antigenically and genetically different (drifted) from the A (H3N2) vaccine component of 2014-15 Northern Hemisphere seasonal influenza vaccines. These early, low VE estimates underscore the need for ongoing influenza prevention and treatment measures. CDC continues to recommend influenza vaccination because the vaccine can still prevent some infections with the currently circulating A (H3N2) viruses as well as other viruses that might circulate later in the season, including influenza B viruses. Even when VE is reduced, vaccination still prevents some illness and serious influenza-related complications, including thousands of hospitalizations and deaths. Persons aged ≥6 months who have not yet been vaccinated this season should be vaccinated, including persons who might already have been ill with influenza this season.