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• Relative VE of high dose to standard dose influenza vaccine was measured in an observational study. • High dose and standard dose recipients differed on several demographic and clinical factors. • Both high and standard dose vaccines were effective against influenza compared to no vaccination. • High dose vaccine provided better protection against influenza A requiring outpatient care. New influenza vaccine formulations are designed to improve vaccine effectiveness and protect those most vulnerable to infection. High dose trivalent inactivated influenza vaccine (HD-IIV3), licensed for ages ≥65 years, produces greater antibody responses and efficacy in clinical trials, but post-licensure vaccine effectiveness (VE) compared to standard dose (SD-IIV3/4) vaccine remains an open question. Using a test-negative, case control design and propensity analyses to adjust for confounding, US Influenza VE Network data from the 2015–2016 through 2018–2019 seasons were analyzed to determine relative VE (rVE) between HD-IIV3 and SD-IIV3/4 among outpatients ≥65 years old presenting with acute respiratory illness. Influenza vaccination status was derived from electronic medical records and immunization registries. Among 3861 enrollees, 2993 (78%) were vaccinated; 1573 (53%) received HD-IIV3 and 1420 (47%) received SD-IIV3/4. HD-IIV3 recipients differed from SD-IIV3/4 recipients by race, previous vaccination, number of outpatient visits in the previous year and timing of vaccination, and were balanced in the propensity model except the timing of vaccination. Compared with no vaccination, significant protection against any influenza A was observed from both HD-IIV3 (VE = 29%; 95%CI = 10%, 44%) and SD-IIV3/4 (VE = 24%; 95%CI = 5%, 39%); rVE = 18% (95%CI = 0%, 33%, SD as referent). When stratified by virus type, against A/H1N1, HD-IIV3 VE was 30% (95%CI = −7%, 54%), SD-IIV3/4 VE was 40% (95%CI = 10%, 61%), and rVE = −32%; (95%CI = −94%, 11%); Against A/H3N2, HD-IIV3 VE was 31% (95%CI = 9%, 47%), SD-IIV3/4 VE was 19% (95%CI = −5%, 37%), and rVE = 27%; (95% CI = 9%, 42%). Among adults ≥65 years of age, recipients of standard and high dose influenza vaccines differed significantly in their characteristics. After adjusting for these differences, high dose vaccine offered more protection against A/H3N2 and borderline significant protection against all influenza A requiring outpatient care during the 2015–2018 influenza seasons. [ABSTRACT FROM AUTHOR]

Influenza is a very important respiratory infectious disease that causes seasonal epidemics and pandemics. A well-organized surveillance system is necessary to monitor and respond effectively to the epidemiologic features of influenza. Korea currently operates a national influenza surveillance system based on the clinical sentinel surveillance system, laboratory sentinel surveillance system, and hospitalization and mortality surveillance system. However, there is a need for a better national surveillance system due to a demand for various pieces of information related to influenza. This article discusses the general aspects of influenza surveillance systems and the future direction of the national influenza surveillance system ofKorea. [ABSTRACT FROM AUTHOR]

Background: This study was performed to investigate the disease burden of seasonal influenza in adults ≥20 years of age in Korea, based on surveillance data from the Hospital-based Influenza Morbidity & Mortality Surveillance (HIMM) network. Materials and methods: The HIMM network is composed of two surveillance systems: emergency room-based and inpatients-based surveillance. A total of ten university hospitals all over the country are included in the surveillance network. The adult catchment population of the HIMM network was calculated by using the data of each hospital and the database of the Health Insurance Review and Assessment Service (HIRA) of Korea. The incidence rates of laboratory-confirmed medically-attended influenza, laboratory-confirmed influenza-related admission and laboratory-confirmed influenza-related death were calculated based on the catchment population. The socioeconomic burden of influenza was estimated using the human capital approach. Results: During the 2013–2014 influenza season, the calculated adult catchment population of the HIMM network was 1,380,000. The incidence of medically-attended laboratory-confirmed influenza infection was 242.8 per 100,000 adults. The incidence of laboratory-confirmed influenza-related admission was 57.9 per 100,000 adults. The incidence of laboratory-confirmed influenza-related death was 3.1 per 100,000 adults. The total socioeconomic cost of 2013–2014 seasonal influenza in Korean adult population was estimated as 125 million USD (1 USD = 1,100 KRW). Conclusion: The disease burden of 2013–2014 seasonal influenza in Korean adult population is very high and indicates that more active prevention and control policies will be needed to decrease the burden. Additional researches will be needed to assess the burden of seasonal influenza in the Korean child population. [ABSTRACT FROM AUTHOR]

Influenza, a highly communicable disease, causes variable epidemics annually and imposes public health problems and socioeconomic burden. In addition to vaccine, antiviral medication has an important role in treatment and prevention of influenza virus infection. As influenza virus is undergoing change of antigenicity and antiviral susceptibility, proper use of antiviral medication is important. This guideline encompasses treatment and chemoprophylaxis with antiviral medications for seasonal influenza based on the current influenza situation in Korea. These recommendations were intended for physicians in all medical specialties who provide care for influenza patients. [ABSTRACT FROM AUTHOR]

The Sofia™ Influenza A + B FIA demonstrated 74.0% sensitivity and 95.4% specificity for influenza A in patients with influenza-like illness in 2012–2013 season. It yielded higher sensitivity than SD Bioline Influenza Ag A/B/A(H1N1/2009) (54.1%) for influenza A ( P < 0.01). The Sofia™ Influenza A + B FIA might be useful for rapid diagnosis of influenza. [ABSTRACT FROM AUTHOR]

Background: After pandemic, A(H1N1)pdm09 is generally known to be associated with younger adults' infection and greater severity than seasonal A(H3N2) but some inconsistences between recent studies exist. Objectives: We aimed to compare the epidemiology and clinical outcomes of A(H1N1)pdm09 and A(H3N2) to verify and consolidate about the knowledge of known differences of subtypes. Methods: Data were retrospectively collected from the hospital‐based influenza morbidity and mortality surveillance in South Korea in nine tertiary care hospitals, from August 31, 2014, to August 25, 2018. Patients with H1N1pdm09 or H3N2 infection admitted in the emergency room or ward were recruited. Results: A total of 1747 patients had influenza A and were divided into two groups those with A(H1N1)pdm09 (n = 240) and those with A(H3N2) (n = 1507). A(H1N1)pdm09 group had younger age (mean age ± standard deviation 50.0 ± 18.8 in H1N1 vs 53.4 ± 21.1 in H3N2, P =.030), lower influenza vaccination (27.9% vs 43.9%, P <.001) and pneumococcal vaccination rates (41.0% vs 51.9%, P <.001), and fewer underlying diseases (67.5% vs 74.0%, P =.035) than the A(H3N2) group. Influenza A subtypes were not associated with pneumonia risk (adjusted odds ratios [AOR] of A(H1N1)pdm09: 0.7 [95% confidence interval [CI]: 0.4‐1.2, P =.172]) and in‐hospital mortality (hazard ratio (HR) of A(H1N1)pdm09: 1.0 (95% CI: 0.3‐3.1, P =.983)). Influenza vaccination reduced in‐hospital mortality in hospitalized patients (HR: 0.3 (95% CI: 0.1‐0.7), P =.005). Conclusions: A(H1N1)pdm09 infection was more common in younger patients without significant difference in pneumonia risk and in‐hospital mortality between subtypes. Influenza vaccination was associated with reduced in‐hospital mortality. [ABSTRACT FROM AUTHOR]

Neuraminidase inhibitors (NAIs) are widely used antiviral drugs for the treatment of humans with influenza virus infections. There have been widespread reports of NAI resistance among seasonal A(H1N1) viruses, and most have been identified in oseltamivir-exposed patients or those treated with other NAIs. Thus, monitoring and identifying NA markers conferring resistance to NAIs--particularly newly introduced treatments--is critical to manage viral infections. Therefore, we screened and identified substitutions conferring resistance to laninamivir by enriching random mutations in the NA gene of the 2009 pandemic influenza A(H1N1)pdm09] followed by deep sequencing of the laninamivir-selected variants. After the generation of single mutants possessing each identified mutation, two A(H1N1)pdm09 recombinants possessing novel NA gene substitutions (ie, D199E and P458T) were shown to confer resistance to more than one NAI. Of note, mutants possessing P458T--which is located outside of the catalytic or framework residue of the NA active site--exhibited highly reduced inhibition by all four approved NAIs. Using MDCK cells, we observed that the in vitro viral replication of the two recombinants was lower compared with WT. Additionally, in infected mice, decreased mortality and/or mean lung viral titers were observed in mutants compared with WT. Reverse mutations to WT were observed in the lung homogenate samples from D199E-infected mice after 3 serial passages. Overall, the novel NA substitutions identified which could possibly emerge in influenza A(H1N1)pdm09 during laninamivir therapy and have altered NAI susceptibility, but the compromised in vitro/in vivo viral fitness may limit viral spreading. [ABSTRACT FROM AUTHOR]

Purpose: Previous studies have demonstrated the immunogenicity and safety of the co-administration of the trivalent inactivated influenza vaccine (IIV3) with the polysaccharide pneumococcal vaccine (PPV) or pneumococcal conjugate vaccine (PCV). However, there is no direct comparison study that evaluates the immunogenicity and safety of IIV3 given concomitantly with PCV13 or PPV23 in the elderly. Materials and Methods: During the 2012-2013 influenza vaccination period, 224 healthy elderly volunteers aged 65 years and older randomly received IIV3 given concomitantly with either PCV13 (PCV13+IIV3) or PPV23 (PPV23+IIV3) in a 1:1 ratio. Serum hemagglutination-inhibiting antibodies for IIV3 were measured at the time of vaccination and 1 month after vaccination. Adverse events were recorded prospectively in a clinical diary during a 7-day period. Results: A total of 220 participants blood samples for analysis of immunogenicity and kept a clinical diary for safety analysis (PCV13+IIV3, n=110; PPV23+IIV3, n=110). One month after vaccination, both groups satisfied the Committee for Medical Products for Human Use criteria for A/H1N1, A/H3N2 and B strains, showing comparable seroprotection rates, seroconversion rates and geometric mean titer fold. The assessments of immunogenicity were similar in both groups. The most common local and systemic reactions were pain at the injection site and generalized myalgia. They were generally mild or moderate in intensity. The adverse events were not statistically different between the two groups. Conclusion: PCV13+IIV3 and PPV23+IIV3 demonstrated similar immunogenicity and safety in the elderly. [ABSTRACT FROM AUTHOR]

The article discusses the results of a study that examines the concurrence of active pulmonary tuberculosis (TB) and influenza A(H1N1)pdm09 virus infection in South Korea. The study shows the sensitivity to anti-TB drugs by all Mycobacterium tuberculosis isolates. Lifetime risk for development of active TB is 5 percent to 10 percent for persons infected with Mycobacterium tuberculosis and increases for those with immunocopromising conditions.

• The effectiveness of repeated influenza vaccination was investigated. • Repeated vaccination was not effective during consecutive flu A/H3N2 epidemics. • About 80% of Korean elderly people receive influenza vaccination annually. • Poor influenza vaccine effectiveness was pronounced among the elderly population. Annually, about 80% of the Korean elderly aged ≥65 years receive influenza vaccination. Repeated annual vaccination has been suggested as an important factor of poor influenza vaccine effectiveness (VE), though reported conflicting results. During the consecutive A/H3N2-dominant influenza seasons between 2012 and 2015, we comparatively evaluated the VE (repeated vs. current season only) against laboratory-confirmed influenza, pneumonia and hospitalization in the elderly aged ≥65 years with influenza-like illness (ILI). Clinical and demographic data were collected prospectively, and vaccination status of prior and current seasons was verified using the immunization registry data of Korean Centers for Disease Control and Prevention. During the first A/H3N2-dominant season in 2012–2013, influenza vaccine showed statistically significant effectiveness against influenza A infection only and when vaccinated in the current season only (VE 53%, 95% CI 15–77). In the latter two seasons (2013–2015 years), the adjusted VE for influenza A was indistinguishable between repeated vaccination and vaccination in the current season only. During consecutive influenza A/H3N2 epidemics, poor influenza vaccine effectiveness may be more pronounced among the elderly population with a high annual vaccine uptake rate. [ABSTRACT FROM AUTHOR]

Background: Influenza and pneumonia are leading causes of morbidity and mortality among the elderly. Although vaccination is a main strategy to prevent these infectious diseases, concerns remain with respect to vaccine effectiveness. Methods: During three influenza seasons (2014–2015, 2015–2016 and 2016–2017), we evaluated the effectiveness of the influenza and pneumococcal vaccines against pneumonia and acute exacerbation of cardiopulmonary diseases among the elderly aged ≥65 years with influenza-like illness (ILI). Demographic and clinical data were collected prospectively. Results: Among 2,119 enrolled cases, 1,302 (61.4%) and 871 (41.1%) received the influenza vaccine and 23-valent pneumococcal polysaccharide vaccine (PPV23), respectively. During an A/H3N2-dominant season with poor influenza vaccine effectiveness (2014–2015 season), neither the influenza vaccine nor PPV23 showed significant effectiveness against pneumonia or acute exacerbation of cardiopulmonary diseases. During seasons with good influenza vaccine effectiveness (2015–2016 and 2016–2017 seasons), the influenza vaccine was effective in preventing pneumonia, but PPV23 was not. In particular, the influenza vaccine was effective in preventing acute exacerbation of heart diseases (75.0%) during the A/H1N1-dominant 2015–2016 season. Conclusion: The influenza vaccine was effective in preventing pneumonia only during vaccine-matched seasons with good effectiveness against circulating influenza viruses. In addition, the influenza vaccine was cardio-protective during a vaccine-matched A/H1N1-dominant season. [ABSTRACT FROM AUTHOR]

In the 2016–2017 season, the A(H3N2) influenza epidemic presented an unusual early peak pattern compared with past seasons in South Korea. The interim vaccine effectiveness (VE) of influenza vaccination in preventing laboratory-confirmed influenza was estimated using test-negative design through the tertiary hospital-based influenza surveillance system in South Korea. From 1 September, 2016 to 7 January, 2017, adjusted VE of influenza vaccination in preventing laboratory-confirmed A(H3N2) was -52.1% (95% confidence interval [CI], -147.2 to 6.4); -70.0% (95% CI, -212.0 to 7.4) in 19–64 years and 4.3% (95% CI, -137.8 to 61.5) in the elderly. Circulating A(H3N2) viruses belonged to the three phylogenetic subclades of 3C.2a, differently to A/Hong Kong/4801/2014, the current vaccine strain. Amino acid substitutions in hemagglutinin of circulating viruses seem to contribute to low VE. In conclusion, interim VE analysis presented that the protection of laboratory-confirmed influenza by seasonal influenza vaccination did not show the statistical significance in South Korea in the 2016–2017 influenza season. [ABSTRACT FROM AUTHOR]

Background: The World Health Organization recommends the surveillance of influenza-like illness (ILI) and severe acute respiratory infection (SARI) to respond effectively to both seasonal influenza epidemics and pandemics. In Korea, the “Hospital-based Influenza Morbidity and Mortality (HIMM)” surveillance system has been operated to monitor ILI and SARI occurrences. Materials and Methods: A multi-center prospective observational study was conducted. Adult patients with acute respiratory infection (ARI) were enrolled during the 2011-12, 2012-2013, and 2013-2014 influenza seasons at the 10 university hospitals using the HIMM surveillance system. With respect to SARI and pneumonia development, risk profiles were analyzed in patients with ARI in Korea. Results: A total of 5,459 cases were eligible for this analysis. Among 5,459 cases with ARI, 2,887 cases (52.9%) were identified that they had influenza infection. Among enrolled cases, 750 cases belonged to the SARI group, while 4,709 cases belonged to the non-SARI group. With respect to pneumonia development, 317 cases were accompanied by pneumonia, and 5,142 cases were not. Multivariate analyses revealed that the following factors were associated with an increased risk of SARI: Old age (≥65 years) (odds ratio [OR] 2.69, 95% confidence interval [CI] 2.2-3.32), chronic heart disease (CHD) (OR 2.24, 95% CI 1.68-2.98), cerebrovascular disease (CVD) (OR 1.49, 95% CI 1.05-2.10), chronic obstructive pulmonary disease (COPD) (OR 2.34, 95% CI 1.48-3.69), asthma (OR 2.33, 95% CI 1.62-3.36), chronic kidney disease (CKD) (OR 2.62, 95% CI 1.73-3.99), chronic liver disease (OR 1.71, 95% CI 1.04-2.81), and autoimmune diseases (OR 2.53, 1.57-4.08). Multivariate analyses revealed that the following factors were independent risk factors for pneumonia development: Old age (≥65 years) (OR 5.71, 95% CI 4.10-7.94), CHD (OR 1.54, 95% CI 1.07-2.22), COPD (OR 2.34, 95% CI 1.48-3.69), asthma (OR 2.33, 95% CI 1.62-3.36), CKD (OR 2.62, 95% CI 1.73-3.99), immunocompromised conditions (OR 3.12, 95% CI 1.47-6.62), and autoimmune diseases (OR 3.35, 95% CI 1.79-6.27). The risk of SARI and pneumonia was increased by the number of concurrent chronic medical conditions. Conclusion: The risk of SARI and pneumonia development among adult patient with ARI was significantly increased by the presence or number of concurrent chronic medical conditions in Korea. [ABSTRACT FROM AUTHOR]

Background Cell culture-derived influenza vaccines (CCIVs) have several important advantages over egg-based influenza vaccines, including shorter production time, better preservation of wild-type virus antigenicity and large-scale production capacity. Methods A randomized, double-blind, phase 3 trial was undertaken to evaluate the immunogenicity and safety of a novel cell culture-derived inactivated, subunit, trivalent influenza vaccine (NBP607, SK Chemicals, Seongnam, Korea) compared to the control vaccine (Agrippal ® S1, Novartis Vaccines and Diagnostics Srl, Siena, Italy) among healthy adults aged 19 years or older (Clinical trial Number— NCT02344134 ). Immunogenicity was determined at pre-vaccination, 1 month and 6 month post-vaccination by the hemagglutination inhibition assay. Solicited and unsolicited adverse events were assessed after vaccination. Results A total of 1156 healthy subjects were recruited. NBP607 met all of the criteria of Committee for Medicinal Products for Human Use (CHMP) at 21 days post-vaccination. Contrary to NBP607, the control vaccine did not satisfy the seroconversion criteria for influenza B irrespective of age. Although the geometric mean titer for each influenza subtype declined gradually, seroprotection rate still remained ≥80% for all subtypes up to six month after NBP607 administration. NBP607 recipients met the seroprotection criteria for all three influenza subtypes up to 6 month post-vaccination. There was no significant difference in the occurrence of adverse events between the NBP607 and control groups. Conclusion NBP607, a novel CCIV, showed excellent immunogenicity that lasted ≥6 months after vaccination and had tolerable safety profiles. In particular, NBP607 was more immunogenic against influenza B compared to the control, an egg-based subunit vaccine. [ABSTRACT FROM AUTHOR]

Objectives: This study aims to identify clinical case definitions of influenza with higher accuracy in patients stratified by age group and influenza activity using hospital-based surveillance system. Methods: In seven tertiary hospitals across South Korea during 2011–2012 influenza season, respiratory specimens were obtained from patients presenting an influenza-like illness (ILI), defined as having fever plus at least one of following symptoms: cough, sore throat or rhinorrhea. Influenza was confirmed by reverse transcriptase-polymerase chain reaction. We performed multivariate logistic regression analyses to identify clinical variables with better relation with laboratory-confirmed influenza, and compared the accuracy of combinations. Results: Over the study period, we enrolled 1417 patients, of which 647 had laboratory-confirmed influenza. Patients with cough, rhinorrhea, sore throat or headache were more likely to have influenza (p<0.05). The most accurate criterion across the study population was the combination of cough, rhinorrhea, sore throat and headache (sensitivity 71.3%, specificity 60.1% and AUROC 0.66). The combination of rhinorrhea, sore throat and sputum during the peak influenza activity period in the young age group showed higher accuracy than that using the whole population (sensitivity 89.3%, specificity 72.1%, and AUROC 0.81). Conclusions: The accuracy of clinical case definitions of influenza differed across age groups and influenza activity periods. Categorizing the entire population into subgroups would improve the detection of influenza patients in the hospital-based surveillance system. [ABSTRACT FROM AUTHOR]

Background: A well-constructed and properly operating influenza surveillance scheme is essential for public health. This study was conducted to evaluate the distribution of respiratory viruses in patients with influenza-like illness (ILI) through the first teaching hospital-based surveillance scheme for ILI in South Korea. Methods: Respiratory specimens were obtained from adult patients (≥18 years) who visited the emergency department (ED) with ILI from week 40, 2011 to week 22, 2012. Multiplex PCR was performed to detect respiratory viruses: influenza virus, adenovirus, coronavirus, respiratory syncytial virus, rhinovirus, human metapneumovirus, parainfluenza virus, bocavirus, and enterovirus. Results: Among 1,983 patients who visited the ED with ILI, 811 (40.9%) were male. The median age of patients was 43 years. Influenza vaccination rate was 21.7% (430/1,983) during the 2011–2012 season. At least one comorbidity was found in 18% of patients. The positive rate of respiratory viruses was 52.1% (1,033/1,983) and the total number of detected viruses was 1,100. Influenza A virus was the dominant agent (677, 61.5%) in all age groups. The prevalence of human metapneumovirus was higher in patients more than 50 years old, while adenovirus was detected only in younger adults. In 58 (5.6%) cases, two or more respiratory viruses were detected. The co-incidence case was identified more frequently in patients with hematologic malignancy or organ transplantation recipients, however it was not related to clinical outcomes. Conclusion: This study is valuable as the first extensive laboratory surveillance of the epidemiology of respiratory viruses in ILI patients through a teaching hospital-based influenza surveillance system in South Korea. [ABSTRACT FROM AUTHOR]

Background: During the 2011/2012 winter influenza season in the Republic of Korea, influenza A (H3N2) was the predominant virus in the first peak period of influenza activity during the second half of January 2012. On the other hand, influenza B was the predominant virus in the second peak period of influenza activity during the second half of March 2012. The objectives of this study were to compare the clinical and epidemiological characteristics of patients with laboratory-confirmed influenza A or influenza B. Methodology/Principal Findings: We analyzed data from 2,129 adult patients with influenza-like illnesses who visited the emergency rooms of seven university hospitals in Korea from October 2011 to May 2012. Of 850 patients with laboratory-confirmed influenza, 656 (77.2%) had influenza A (H3N2), and 194 (22.8%) influenza B. Age, and the frequencies of cardiovascular disorders, diabetes, hypertension were significantly higher in patients with influenza A (H3N2) (P<0.05). The frequencies of leukopenia or thrombocytopenia in patients with influenza B at initial presentation were statistically higher than those in patients with influenza A (H3N2) (P<0.05). The rate of hospitalization, and length of hospital stay were statistically higher in patients with influenza A (H3N2) (P<0.05), and of the 79 hospitalized patients, the frequency of diabetes, hypertension, cases having at least one of the comorbid conditions, and the proportion of elderly were significantly higher in patients with influenza A (H3N2) (P<0.05). Conclusions: The proportion of males to females and elderly population were significantly higher for influenza A (H3N2) patients group compared with influenza B group. Hypertension, diabetes, chronic lung diseases, cardiovascular disorders, and neuromuscular diseases were independently associated with hospitalization due to influenza. Physicians should assess and treat the underlying comorbid conditions as well as influenza viral infections for the appropriate management of patients with influenza. [ABSTRACT FROM AUTHOR]

Purpose: Women who are pregnant, planning to become pregnant in the influenza season or caring for infant 6-59 months of age are identified as priority groups for influenza vaccination. Vaccination rate is presumed to be low in those women. The purpose of this study was to investigate perceptions of childbearing age women about influenza vaccination. Materials and Methods: Childbearing age women visiting the department of Obstetrics and Gynecology in 3 University hospitals in Seoul and Gyeonggi-do province were surveyed. Individual interviews were performed to them with questionnaire for 2 months from April to May 2012. Demographic data, Immunization history, general understanding and factors associated with vaccination were asked. Results: Three hundred fifty-five (71.0%) of total 500 reproductive age women had the experience of influenza vaccination. Among 343 women who has been pregnant at least once, 48 women (16.4%) had vaccination during pregnancy, and 46 of them got vaccination since 2009. One hundred ninety women of total 500 women responded that they would get vaccination if pregnant in the next influenza season (38.0%). In multivariate analysis, statistically significant factors associated with plans of influenza vaccination in pregnancy were as follows: experience of childbirth (odds ratio [OR], 1.97; 95% CI, 1.32 to 2.93), high level of education (OR, 1.96; 95% CI, 1.22 to 3.15), previous influenza vaccination (OR, 1.88; 95% CI, 1.17 to 3.01). Conclusion: Influenza vaccine coverage on childbearing age women including pregnant women is low because of misperception of vaccination during pregnancy. It is necessary for healthcare provider to correct misunderstanding and to recommend vaccination actively. [ABSTRACT FROM AUTHOR]

Abstract: The 2009 influenza pandemic was caused by a novel triple-reassortant influenza A/H1N1 virus that was further recombined with a Eurasian pig flu virus. Vaccination is a key countermeasure for disease; however, little data assessing vaccine effectiveness (VE) against the pandemic H1N1 virus are available. We conducted a matched case–control study to assess effectiveness of the 2009 influenza A/H1N1 monovalent vaccine against laboratory-confirmed, medically attended influenza patients. Subjects included in the study were ≥10 years of age and were treated at five university hospitals in the Republic of Korea (ROK) from December 2009 through March 2010. For subjects visiting outpatient clinics with influenza-like illness (ILI), real time reverse transcription polymerase chain reaction (rRT-PCR) was used to diagnose 2009 H1N1 influenza virus infection. Subjects with positive rRT-PCR were classified as cases, while those testing negative were controls. A valid vaccination corresponded to ≥14 days between receiving a dose of vaccine and symptom onset. Overall, 416 ILI subjects were analyzed, and 60 (14.4%) were vaccinated with the 2009 influenza A/H1N1 monovalent vaccine. The overall VE against pandemic 2009 A/H1N1 virus illness after adjustment for age group and presence of chronic medical conditions was 73.4% (95% confidence interval [CI]=49.1–86.1%). Both vaccine formulations (unadjuvanted and MF-59 adjuvanted) showed a statistically significant VE. In conclusion, the 2009 influenza A/H1N1 monovalent vaccine was substantially protective against pandemic influenza in the ROK during the 2009–2010 season. [Copyright &y& Elsevier]

Abstract: In a pandemic, the development of an effective influenza vaccine is the most important subject from the view of public health. This study was performed to evaluate the immunogenicity and safety of inactivated, monovalent H1N1 2009 vaccine (Green Cross Corporation, Yongin, Korea) among healthy adults aged 19–64 years (Group 1) and the elderly aged ≥65 years (Group 2) in a two-dose regimen, 21 days apart. At baseline, 28 of 454 participants (6.1%) had hemagglutination-inhibition titers of ≥1:40 with no significant difference between age groups (p =0.27). There was an apparent dose-dependent antibody response; participants receiving the dose of 30μg hemagglutinin (HA) showed higher geometric mean titers (GMTs) than the 15μg HA group in both age groups. Despite the rates of seroprotection and seroconversion were significantly higher with 30μg HA formulation than 15μg HA formula in Group 2, there was no definite difference in Group 1 irrespective of vaccine formula. Significant GMT elevation after the second dose was not noted in either age group, regardless vaccine formulations. No deaths, vaccine-related serious adverse events, or immediate unsolicited adverse reactions occurred during the study periods. [Copyright &y& Elsevier]

Abstract: The elderly have been considered as the priority group for influenza vaccination, but their influenza vaccine-induced antibody was believed to decline more rapidly. Long-term immunogenicity of the influenza vaccine among the elderly was evaluated as compared to young adults. Serum hemagglutinin inhibition (HI) titers were determined at pre- and post-vaccination periods (at 1, 6, and 12 months after vaccination). Of the 1018 subjects, 716 (70.3%) were followed up during a 12-month period. Seroprotection rates at 1 month post-vaccination ranged from 70.1% to 90.3% depending on the age group and influenza vaccine virus strain. At 6 months post-vaccination, seroprotection rates for all three strains had declined significantly in adults ≥65 years (P <0.01), but still met the EMEA criteria. Low pre-vaccination HI titer (<1:40) and advanced age were associated with early decline of HI titers, falling below seroprotective levels around 6 months after vaccination. [Copyright &y& Elsevier]

Baloxavir marboxil (BXM) treatment-emergent polymerase acid (PA) I38X amino acid substitution (AAS) in the resistant variants of influenza viruses raise concerns regarding their emergence and spread. This study investigated the impact of 1 or 5 mg/kg BXM and 25 mg/kg oseltamivir phosphate (OS) (single or combination therapy) on the occurrence of resistance-related substitutions during the sequential lung-to-lung passages of AH1N1)pdm09 virus in mice. Deep sequencing analysis revealed that 67% (n = 4/6) of the population treated with BXM single therapy (1 or 5 mg/kg) possessed the treatment-emergent PA-I38X AAS variants (I38T, I38S, and I38V). Notably, BXM-OS combination therapy impeded PA-I38X AAS emergence. Although the doses utilized in the mouse model may not be directly translated into the clinically equivalent doses of each drugs, these findings offer insights toward alternative therapies to mitigate the emergence of influenza antiviral resistance. • Baloxavir marboxil single treatment increases the rate of selection of PA-I38X resistant variants in a mouse model. • The treatment-emergent viral populations with resistant variants acquired reduced susceptibility to BXM. • BXM-OS combination therapy impeded the occurrence of PA-I38X resistant variants in in vivo. [ABSTRACT FROM AUTHOR]