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Background Randomized trials conducted in low- and middle-income settings demonstrated efficacy of influenza vaccination during pregnancy against influenza infection among infants <6 months of age. However, vaccine effectiveness (VE) estimates from settings with different population characteristics and influenza seasonality remain limited. Methods We conducted a test-negative study in Ontario, Canada. All influenza virus tests among infants <6 months from 2010 to 2019 were identified and linked with health databases to ascertain information on maternal-infant dyads. VE was estimated from the odds ratio for influenza vaccination during pregnancy among cases versus controls, computed using logistic regression with adjustment for potential confounders. Results Among 23 806 infants tested for influenza, 1783 (7.5%) were positive and 1708 (7.2%) were born to mothers vaccinated against influenza during pregnancy. VE against laboratory-confirmed infant influenza infection was 64% (95% confidence interval [CI], 50%–74%). VE was similar by trimester of vaccination (first/second, 66% [95% CI, 40%–80%]; third, 63% [95% CI, 46%–74%]), infant age at testing (0 to <2 months, 63% [95% CI, 46%–75%]; 2 to <6 months, 64% [95% CI, 36%–79%]), and gestational age at birth (≥37 weeks, 64% [95% CI, 50%–75%]; < 37 weeks, 61% [95% CI, 4%–86%]). VE against influenza hospitalization was 67% (95% CI, 50%–78%). Conclusions Influenza vaccination during pregnancy offers effective protection to infants <6 months, for whom vaccines are not currently available. [ABSTRACT FROM AUTHOR]

Background Older adults are recommended to receive influenza vaccination annually, and many use statins. Statins have immunomodulatory properties that might modify influenza vaccine effectiveness (VE) and alter influenza infection risk. Methods Using the test-negative design and linked laboratory and health administrative databases in Ontario, Canada, we estimated VE against laboratory-confirmed influenza among community-dwelling statin users and nonusers aged ≥66 years during the 2010–2011 to 2018–2019 influenza seasons. We also estimated the odds ratio for influenza infection comparing statin users and nonusers by vaccination status. Results Among persons tested for influenza across the 9 seasons, 54 243 had continuous statin exposure before testing and 48 469 were deemed unexposed. The VE against laboratory-confirmed influenza was similar between statin users and nonusers (17% [95% confidence interval, 13%–20%] and 17% [13%–21%] respectively; test for interaction, P =.87). In both vaccinated and unvaccinated persons, statin users had higher odds of laboratory-confirmed influenza than nonusers (odds ratios for vaccinated and unvaccinated persons 1.15 [95% confidence interval, 1.10–1.21] and 1.15 [1.10–1.20], respectively). These findings were consistent by mean daily dose and statin type. VE did not differ between users and nonusers of other cardiovascular drugs, except for β-blockers. We did not observe that vaccinated and unvaccinated users of these drugs had increased odds of influenza, except for unvaccinated β-blocker users. Conclusions Influenza VE did not differ between statin users and nonusers. Statin use was associated with increased odds of laboratory-confirmed influenza in vaccinated and unvaccinated persons, but these associations might be affected by residual confounding. [ABSTRACT FROM AUTHOR]

Background Older adults are at increased risk of mortality from influenza infections. We estimated influenza vaccine effectiveness (VE) against mortality following laboratory-confirmed influenza. Methods Using a test-negative design study and linked laboratory and health administrative databases in Ontario, Canada, we estimated VE against all-cause mortality following laboratory-confirmed influenza for community-dwelling adults aged >65 years during the 2010–2011 to 2015–2016 influenza seasons. Results Among 54 116 older adults tested for influenza across the 6 seasons, 6837 died within 30 days of specimen collection. Thirteen percent (925 individuals) tested positive for influenza, and 50.6% were considered vaccinated for that season. Only 23.2% of influenza test-positive cases had influenza recorded as their underlying cause of death. Before and after multivariable adjustment, we estimated VE against all-cause mortality following laboratory-confirmed influenza to be 20% (95% confidence interval [CI], 8%–30%) and 20% (95% CI, 7%–30%), respectively. This estimate increased to 34% after correcting for influenza vaccination exposure misclassification. We observed significant VE against deaths following influenza confirmation during 2014–2015 (VE = 26% [95% CI, 5%–42%]). We also observed significant VE against deaths following confirmation of influenza A/H1N1 and A/H3N2, and against deaths with COPD as the underlying cause. Conclusions These results support the importance of influenza vaccination in older adults, who account for most influenza-associated deaths annually. [ABSTRACT FROM AUTHOR]

Background Vaccine effectiveness (VE) studies provide essential evidence on waning vaccine-derived immunity, a major threat to pertussis control. We evaluated how study design affects estimates by comparing 2 case-control studies conducted in Ontario, Canada. Methods We compared results from a test-negative design (TND) with a frequency-matched design (FMD) case-control study using pertussis cases from 2005–2015. In the first study, we identified test-negative controls from the public health laboratory that diagnosed cases and, in the second, randomly selected controls from patients attending the same physicians that reported cases, frequency matched on age and year. We compared characteristics of cases and controls using standardized differences. Results In both designs, VE estimates for the early years postimmunization were consistent with clinical trials (TND, 84%; FMD, 89% at 1–3 years postvaccination) but diverged as time since last vaccination increased (TND, 41%; FMD, 74% by 8 years postvaccination). Overall, we observed lower VE and faster waning in the TND than the FMD. In the TND but not FMD, controls differed from cases in important confounders, being younger, having more comorbidities, and higher healthcare use. Differences between the controls of each design were greater than differences between cases. TND controls were more likely to be unvaccinated or incompletely vaccinated than FMD controls (P  < .001). Conclusions The FMD adjusted better for healthcare-seeking behavior than the TND. Duration of protection from pertussis vaccines is unclear because estimates vary by study design. Caution should be exercised by experts, researchers, and decision makers when evaluating evidence on optimal timing of boosters. [ABSTRACT FROM AUTHOR]

Background Adolescents make decisions about their own vaccinations and will be the childhood vaccine decision makers of tomorrow. It is therefore essential to educate adolescents about the risks of vaccine-preventable diseases and immunization safety. This study evaluated the impact of an interactive education initiative among adolescents at a high school in North Bay Ontario. Methods An anonymized questionnaire to assess students' knowledge, attitudes and beliefs about immunization and vaccine-preventable diseases was administered before and after delivering an interactive session. Chi-squared and Kruskal-Wallis tests were performed to test for differences between pre and post responses. Results The intervention increased the students' awareness that measles is a disease that affects their generation (P  < 0.05). Improvements were also noted in the perceived risk of pertussis (P  < 0.05) and tetanus (0.05). After the session, respondents were also more willing to participate with their parents in decisions affecting their healthcare (P  < 0.05). Students' perception of vaccine safety also improved (P  < 0.001). Conclusions Post survey results suggest that the interactive educational intervention had a positive effect on the adolescents' perceptions and attitudes towards immunization. Further research is required to determine the impact of this type of intervention on adolescents' future decision-making with respect to immunization. [ABSTRACT FROM AUTHOR]

Background Many studies assume that the serologic correlate of protection from measles disease is 120 mIU/mL. We systematically reviewed the literature to examine the evidence supporting this correlate of protection. Methods We searched peer-reviewed and gray literature for articles reporting a measles correlate of protection. We excluded studies focusing on special populations, infants aged <9 months, and those using animal models or nonstandard vaccines or administration routes. We extracted and synthesized data from full-text articles that met inclusion criteria. Results We screened 14 778 articles and included 5 studies in our review. The studies reported either preexposure antibody concentrations of individuals along with a description of symptoms postexposure, or the proportion of measles cases that had preexposure antibody concentrations above a threshold of immunity specified by the authors. Some studies also described secondary antibody responses upon exposure. The variation in laboratory methods between studies made comparisons difficult. Some of the studies that assumed 120 mIU/mL as a correlate of protection identified symptomatic individuals with preexposure titers exceeding this threshold. Conclusions Our findings underscore the scant data upon which the commonly used 120 mIU/mL measles threshold of protection is based, suggesting that further work is required to characterize the measles immunity threshold. [ABSTRACT FROM AUTHOR]

We conducted a systematic review to describe the frequency of mild, atypical, and asymptomatic infection among household contacts of pertussis cases and to explore the published literature for evidence of asymptomatic transmission. We included studies that obtained and tested laboratory specimens from household contacts regardless of symptom presentation and reported the proportion of cases with typical, mild/atypical, or asymptomatic infection. After screening 6789 articles, we included 26 studies. Fourteen studies reported household contacts with mild/atypical pertussis. These comprised up to 46.2% of all contacts tested. Twenty-four studies reported asymptomatic contacts with laboratory-confirmed pertussis, comprising up to 55.6% of those tested. Seven studies presented evidence consistent with asymptomatic pertussis transmission between household contacts. Our results demonstrate a high prevalence of subclinical infection in household contacts of pertussis cases, which may play a substantial role in the ongoing transmission of disease. Our review reveals a gap in our understanding of pertussis transmission. [ABSTRACT FROM AUTHOR]

Background: Annual influenza immunization is recommended for people with chronic obstructive pulmonary disease (COPD) by all major COPD clinical practice guidelines. We sought to determine the seasonal influenza vaccine effectiveness (VE) against laboratory-confirmed influenza-associated hospitalizations among older adults with COPD.Methods: We conducted a test-negative study of influenza VE in community-dwelling older adults with COPD in Ontario, Canada using health administrative data and respiratory specimens collected from patients tested for influenza during the 2010-11 to 2015-16 influenza seasons. Influenza vaccination was ascertained from physician and pharmacist billing claims. Multivariable logistic regression was used to estimate the adjusted odds ratio of influenza vaccination in people with, compared to those without, laboratory-confirmed influenza.Results: Receipt of seasonal influenza vaccine was associated with an adjusted 22% (95% confidence interval [CI], 15%-27%) reduction in laboratory-confirmed influenza-associated hospitalization. Adjustment for potential misclassification of vaccination status increased this to 43% (95% CI, 35%-52%). Vaccine effectiveness was not found to vary by patient- or influenza-related variables.Conclusions: During the studied influenza seasons, influenza vaccination was at least modestly effective in reducing laboratory-confirmed influenza-associated hospitalizations in people with COPD. The imperfect effectiveness emphasizes the need for better influenza vaccines and other preventive strategies. [ABSTRACT FROM AUTHOR]

Despite robust evidence that routine immunization is effective and safe, some parents refuse some or all vaccines for their children. In 2007, concern that Canadian paediatricians and family physicians might be considering dismissal of vaccine refusers from their practices prompted an ethical, legal, and public health analysis which concluded that dismissal was professionally problematic. We now reassess this important issue in the Canadian context updating ethical, legal, and public health considerations highlighting changes since 2007. In light of the recent strengthening of Ontario's school immunization requirements that include stiffer steps to qualify for a medical, conscience, or religious belief exemption, physicians and health care workers may be under more pressure from vaccine refusers in their practice leading some to contemplate dismissal or even consider no longer offering immunizations at all in their practice. Given the challenges that vaccine refusers may present, we offer an overview for managing vaccine refusal by parents/patients in a medical practice. [ABSTRACT FROM AUTHOR]

Background Barriers and facilitators of mobile app adoption are not known. This study examined usage of a new Pan-Canadian immunization app to identify factors that contributed to usage. Methods Women in their third trimester of pregnancy or had given birth in the previous 3 months were recruited from a hospital obstetrical unit. Fifty-five participants were instructed to download the ImmunizeCA app. After at least 6 months, 10 interviews were conducted, transcribed and coded. Themes identified were compared with aggregate ImmunizeCA usage data (n = 74 212 users). Results Facilitators included features that address logistical challenges, improved convenience and information access. Barriers included absence of system integration. Concerns regarding the privacy and security of personal health information were not an inhibitor as long as best practices are followed. Google Analytics data on usage supported qualitative findings. Conclusion Future studies should evaluate the quantitative impact of factors we identified on app uptake and usage. Subsequent mobile app studies may benefit from the use of analytic data as they were found to be effective in helping to validate qualitative data derived from interviews with study participants. [ABSTRACT FROM AUTHOR]

Summary of Key Points. Although relatively rare, invasive meningococcal disease continues to be a health concern, especially in young children. This systematic review clearly delineates both the near- and long-term morbidities that can occur after, and persist beyond, the period of acute illness. Background. Although rare, invasive meningococcal disease (IMD) continues to be a health concern in highincome countries because of its severe morbidity and relatively high case fatality rate, especially in young children. However, studies measuring sequelae of IMD across the spectrum of invasive syndromes have not been systematically reviewed. We conducted a systematic review of sequelae attributable to IMD and quality of life (QoL) in IMD survivors in high-income countries. Methods. We searched Medline, Embase, and HealthSTAR for primary studies that assessed sequelae or QoL in individuals of any age with and without IMD. Two independent reviewers screened articles, abstracted data, and performed quality appraisal. The findings were summarized qualitatively. Results. Of 1884 citations screened, 17 studies were included. The most commonly assessed sequelae were hearing impairment, cognitive impairment, and psychological problems. In general, children with IMD had a greater incidence of hearing loss and psychological disorders, including attention-deficit/hyperactivity disorder. However, its effects on intelligence in children remain unclear. No statistical differences in overall cognitive function in adults were reported. The odds of death were significantly increased with IMD at hospital discharge and up to 30 years after disease. Lower overall QoL was observed in those who had IMD versus controls. Conclusions. The results of this systematic review delineate both the short- and long-term morbidities that can occur after, and persist beyond, the period of acute illness. A better understanding of the full spectrum of IMD sequelae is critical for assessing the burden of IMD and supporting healthcare planning and decision making in light of new vaccines. [ABSTRACT FROM AUTHOR]

Immunization registries or information systems are critical to improving the quality and evaluating the ongoing success of immunization programs. However, the completeness of these systems is challenged by a myriad of factors including the fragmentation of vaccine administration, increasing mobility of individuals, new vaccine development, use of multiple products, and increasingly frequent changes in recommendations. Mobile technologies could offer a solution, which mitigates some of these challenges. Engaging individuals to have more control of their own immunization information using their mobile devices could improve the timeliness and accuracy of data in central immunization information systems. Other opportunities presented by mobile technologies that could be exploited to improve immunization information systems include mobile reporting of adverse events following immunization, the capacity to scan 2D barcodes, and enabling bidirectional communication between individuals and public health officials. Challenges to utilizing mobile solutions include ensuring privacy of data, access, and equity concerns, obtaining consent and ensuring adoption of technology at sufficiently high rates. By empowering individuals with their own health information, mobile technologies can also serve as a mechanism to transfer immunization information as individuals cross local, regional, and national borders. Ultimately, mobile enhanced immunization information systems can help realize the goal of the individual, the healthcare provider, and public health officials always having access to the same immunization information. [ABSTRACT FROM AUTHOR]

Pertussis (whooping cough) is a respiratory disease caused by the bacterium Bordetella pertussis. Despite the implementation of immunization programs and high vaccine coverage in most jurisdictions, pertussis is still one of the most common vaccine-preventable diseases, suggesting that the current vaccines and immunization schedules have not been sufficiently effective. Several factors are thought to contribute to this. The acellular pertussis vaccine that has been used in many jurisdictions since the 1990s is less effective than the previously used whole-cell vaccine, with immunity waning over time. Both whole-cell and acellular pertussis vaccines are effective at reducing disease severity but not transmission, resulting in outbreaks in vaccinated cohorts. In this review, we discuss various limitations of the current approaches to protection from pertussis and outline various options for reducing the burden of pertussis on a population level. [ABSTRACT FROM AUTHOR]

Although the benefits of influenza vaccines for preventing serious influenza outcomes in elderly adults are uncertain, the results of this study suggest that the 2010–2011 influenza vaccine was 42% effective in reducing laboratory-confirmed influenza hospitalizations in this high-risk population.Background. Although annual influenza immunization is recommended for adults aged ≥65 years due to the substantial burden of illness, the evidence base for this recommendation is weak. Prior observational studies that examined influenza vaccine effectiveness against nonspecific serious outcomes suffered from selection bias and the lack of laboratory confirmation for influenza infection. The objective of this study was to determine the effectiveness of the 2010–2011 seasonal influenza vaccine against laboratory-confirmed influenza hospitalizations among community-dwelling elderly adults, a serious and highly specific outcome.Methods. We conducted a test-negative study of community-dwelling adults aged >65 years in Ontario, Canada. Respiratory specimens collected between 1 December 2010 and 30 April 2011 from patients admitted to acute care hospitals were tested for influenza using nucleic acid amplification techniques. Influenza vaccination was ascertained from physician billing claims through linkage to health administrative datasets.Results. Receipt of the 2010–2011 seasonal influenza vaccine was associated with a 42% (95% confidence interval, 29%–53%) reduction in laboratory-confirmed influenza hospitalizations. Vaccine effectiveness estimates were consistent across age groups, by sex, and regardless of outcome severity, timing of testing, and when considering individuals vaccinated <7 or <14 days prior to admission as unvaccinated.Conclusions. Results of this study will better inform decision making regarding influenza vaccination of elderly adults. Similar analyses are needed annually due to antigenic drift and frequent changes in influenza vaccine composition. The linkage of routinely collected laboratory testing and health administrative data represents an efficient method for estimating influenza vaccine effectiveness that complements prospective studies. [ABSTRACT FROM PUBLISHER]

The population-level safety benefits of the acellular pertussis vaccine may have been underestimated because only specific adverse events were considered, not overall impact on health services utilization. Using the Vaccine and Immunization Surveillance in Ontario (VISION) system, the authors analyzed data on 567,378 children born between April 1994 and March 1996 (before introduction of acellular pertussis vaccine) and between April 1998 and March 2000 (after introduction of acellular pertussis vaccine) in Ontario, Canada. Using the self-controlled case series study design, they examined emergency room visits and hospital admissions occurring after routine pediatric vaccinations. The authors determined the relative incidence of events taking place before introduction of the acellular vaccine versus after introduction by calculating relative incidence ratios (RIRs). The observed RIRs demonstrated a highly statistically significant reduction in relative incidence after introduction of the acellular vaccine. RIRs for vaccine administered at ages 2, 4, 6, and 18 months were 1.82 (95% confidence interval (CI): 1.64, 2.01), 1.91 (95% CI: 1.71, 2.13), 1.54 (95% CI: 1.38, 1.72), and 1.51 (95% CI: 1.34, 1.69), respectively, comparing event rates before the introduction of acellular vaccine with those after introduction. The authors estimated that approximately 90 emergency room visits and 9 admissions per month were avoided by switching to the acellular vaccine, which is a 38-fold higher impact than when they considered only admissions for febrile and afebrile convulsions. Future analyses comparing vaccines for safety should examine specific endpoints and general health services utilization. [ABSTRACT FROM PUBLISHER]

We propose a multicomponent surveillance platform to incorporate genotypic, phenotypic, and epidemiologic indicators into the assessment of influenza virus, new variant circulation, vaccine relatedness, and vaccine effectiveness. The utility of such a system is illustrated for the 2010–2011 season in Canada.Background. During the 2010–2011 winter, a large number of outbreaks due to influenza A/H3N2 at long-term care facilities, including higher-than-expected attack rates among vaccinated staff, were reported in some regions of Canada. Interim analysis from the community-based sentinel surveillance system showed circulating H3N2 variants and suboptimal vaccine effectiveness (VE), assessed here for the entire season's data set.Methods. Nasal/nasopharyngeal swabs and epidemiologic details were collected from patients presenting to sentinel sites within 7 days of onset of influenza-like illness. Cases tested positive for influenza by real-time reverse-transcription polymerase chain reaction; controls tested negative. Odds ratios for medically attended, laboratory-confirmed influenza in vaccinated vs nonvaccinated participants were used to derive adjusted VE. Viruses were characterized by hemagglutination inhibition (HI), and the hemagglutinin genes of a subset were sequenced to explore vaccine relatedness.Results. Final 2010–2011 VE analysis included 1718 participants (half aged 20–49 years), 93 with A(H1N1)pdm09, 408 with A/H3N2, and 199 with influenza B. Among adults aged 20–49 years, adjusted VE was 65% (95% confidence interval [CI], 8%–87%) for A(H1N1)pdm09 and 66% (95% CI, 10%–87%) for influenza B. Vaccine effectiveness was substantially lower for A/H3N2, at 39% (95% CI, 0%–63%). Phylogenetic analysis identified 2 circulating H3N2 variant clades, A/HongKong/2121/2010 (87%) and A/Victoria/208/2009 (11%), bearing multiple amino acid substitutions at antigenic sites (12 and 8, respectively) compared with the H3N2 vaccine component used in Canada (A/Victoria/210/2009[NYMC X-187]). However, HI characterized all H3N2 isolates as well matched to the vaccine.Conclusions. Public health observations of increased facility H3N2 outbreaks were consistent with the sentinel network's detection of genetic variants and suboptimal VE but not with conventional HI characterization. We highlight the utility of a multicomponent sentinel surveillance platform that incorporates genotypic, phenotypic, and epidemiologic indicators into the assessment of influenza virus, new variant circulation, vaccine relatedness, and VE. [ABSTRACT FROM PUBLISHER]

Objectives. To estimate influenza vaccine effectiveness (VE) for the 2007–2008 season and assess the sentinel surveillance system in Canada for monitoring virus evolution and impact on VE.Methods. Nasal/nasopharyngeal swabs and epidemiologic details were collected from patients presenting to a sentinel physician within 7 days of influenza-like illness onset. Cases tested positive for influenza A/B virus by real-time polymerase chain reaction; controls tested negative. Hemagglutination inhibition (HI) and gene sequencing explored virus relatedness to vaccine. VE was calculated as 1 minus the odds ratio for influenza in vaccinated versus nonvaccinated participants, with adjustment for confounders.Results. Of 1425 participants, 21% were vaccinated. Influenza virus was detected in 689 (48%), of which isolates from 663 were typed/subtyped: 189 (29%) were A/H1, 210 (32%) were A/H3, and 264 (40%) were B. Of A/H1N1 isolates, 6% showed minor HI antigenic mismatch to vaccine, with greater variation based on genetic identity. All A/H3N2 isolates showed moderate antigenic mismatch, and 98% of influenza B virus isolates showed major lineage-level mismatch to vaccine. Adjusted VE for A/H1N1, A/H3N2, and B components was 69% (95% confidence interval [CI], 44%–83%), 57% (95% CI, 32%–73%), and 55% (95% CI, 32%–70%), respectively, with an overall VE of 60% (95% CI, 45%–71%).Conclusions. Detailed antigenic and genotypic analysis of influenza viruses was consistent with epidemiologic estimates of VE showing cross-protection. A routine sentinel surveillance system that combines detailed virus and VE monitoring annually, as modeled in Canada, may guide improved vaccine selection and protection. [ABSTRACT FROM AUTHOR]

The article discusses that regular boosting of adults with tetanus, diphtheria, and a cellular pertussis (Tdap) boosters is a possible strategy that could be implemented relatively easily within existing immunization programs. It mentions that increasing evidence for short-lived protection in adolescents leads to the question of how well pertussis vaccines actually work in adults. It also mentions that adults are likely to have milder symptoms than children.

Interventions for parvovirus B19 infection need to balance the low risk of infection at a population level with the potential for serious adverse outcome for particular groups, notably the fetus, people with haemoglobinopathies and the immunocompromised. This guidance aims to assist the local decision-making process to be as evidence-based as the available evidence allows. [ABSTRACT FROM PUBLISHER]

Background: Many studies assume that the serologic correlate of protection from measles disease is 120 mIU/mL. We systematically reviewed the literature to examine the evidence supporting this correlate of protection.Methods: We searched peer-reviewed and gray literature for articles reporting a measles correlate of protection. We excluded studies focusing on special populations, infants aged <9 months, and those using animal models or nonstandard vaccines or administration routes. We extracted and synthesized data from full-text articles that met inclusion criteria.Results: We screened 14 778 articles and included 5 studies in our review. The studies reported either preexposure antibody concentrations of individuals along with a description of symptoms postexposure, or the proportion of measles cases that had preexposure antibody concentrations above a threshold of immunity specified by the authors. Some studies also described secondary antibody responses upon exposure. The variation in laboratory methods between studies made comparisons difficult. Some of the studies that assumed 120 mIU/mL as a correlate of protection identified symptomatic individuals with preexposure titers exceeding this threshold.Conclusions: Our findings underscore the scant data upon which the commonly used 120 mIU/mL measles threshold of protection is based, suggesting that further work is required to characterize the measles immunity threshold. [ABSTRACT FROM AUTHOR]