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Background: Despite being a vaccine-preventable disease, influenza remains a major public health threat with vaccine safety concerns reducing vaccine acceptability. Immune responses to vaccines and adverse events may differ between males and females, but most studies do not report results by sex. Using data from clinical trials, we explored sex differences in adverse events following seasonal influenza vaccines., Methods: We obtained data for phase III randomised controlled trials identified through a systematic review and clinical trials registries, and performed a two-stage meta-analysis. Risk ratios (RR) and 95% confidence intervals (95% CI) comparing solicited reactions in females versus males were pooled using the Mantel-Haenszel method and a random-effects model. We used the ROBINS-I tool to assess risk of bias and the I 2 statistic for heterogeneity. Main analysis was stratified by age: 18-64 years and ≥65 years., Results: The dataset for this analysis included 34 343 adults from 18 studies (12 with individual-level data and 6 with aggregate data). There was a higher risk of injection site reactions in females compared with males for both younger and older participants, with RRs of 1.29 (95% CI 1.21 to 1.37) and 1.43 (95% CI 1.28 to 1.60), respectively. Higher risk in females was also observed for systemic reactions, with RRs of 1.25 (95% CI 1.20 to 1.31) and 1.27 (95% CI 1.20 to 1.34) for younger and older participants, respectively. We also observed elevated risks of severe reactions in females, with a higher RR in younger versus older participants for systemic reactions (RRs 2.12 and 1.48, p=0.03, I 2 =79.7%). RRs were not found to vary between quadrivalent and trivalent vaccines., Conclusion: This meta-analysis suggested a higher risk of solicited reactions following influenza vaccines for females compared with males, irrespective of age and vaccine type. Transparent communication of this risk could increase the trust in vaccines and limit vaccine hesitancy. Future studies should report results stratified by sex and explore the role of gender in the occurrence of adverse events., Competing Interests: Competing interests: All authors have completed the ICMJE uniform disclosure form at http://www.icmje.org/disclosure-of-interest/ and declare: no support from any organisation for the submitted work. MS has been an investigator on projects funded by GlaxoSmithKline, Merck, Moderna, Pfizer, Sanofi-Pasteur, Seqirus, Symvivo and VBI Vaccines. All funds have been paid to his institute, and he has not received any personal payments; there are no other relationships or activities that could appear to have influenced the submitted work., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Neuraminidase inhibitors (NAIs) are likely part of the rapid response and control in influenza pandemics and institutional outbreaks. We conducted a systematic review to appraise the current evidence on the use of NAIs among healthcare workers in the context of an influenza pandemic.

Introduction: Seasonal influenza is an important cause of morbidity and mortality, despite being vaccine-preventable. Sex factors (genes and hormones) seem to impact individuals' susceptibility to infectious diseases and their response to vaccination. However, most vaccine studies do not explicitly assess sex differences in vaccine response, but rather adjust for sex., Methods: We conducted a systematic review to analyze immunogenicity, efficacy, effectiveness and/or safety of seasonal influenza vaccine data stratified by sex. We searched PubMed, EMBASE, CINAHL, Web of Science and clinicaltrials.gov for observational studies and phase III/IV trials from January 1990 to June 2018, published in English or French. Two reviewers independently screened all references, then proceeded to data extraction and quality assessment using the Cochrane tools (RoB and ROBINS-I) on included studies., Results: Of the 5,745 citations retrieved, 46 studies were included in the SR. Overall, 18 studies assessed immunogenicity, 1 estimated efficacy, 6 measured effectiveness and 25 evaluated safety of seasonal influenza vaccine in females and males (four studies reported on two sex-stratified outcomes concomitantly)., Conclusion: No clear conclusion could be drawn regarding the effect of sex on the immunogenicity and effectiveness of seasonal influenza vaccine, but higher rates of adverse events following immunization (AEFIs) were reported in females. The heterogeneity of data and studies' low quality prevented us from conducting a meta-analysis. There is a need to emphasize on the appropriate use of the terms sex and gender in biomedical research. Evidence of higher quality is needed to better understand sex differences in response to influenza vaccine., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Introduction: Although a vaccine-preventable disease, influenza causes approximately 3-5 million cases of severe illness and about 290,000-650,000 deaths worldwide, which occur primarily among people 65 years and older. Nonetheless, prevention of influenza and its complications rely mainly on vaccination. We aimed to systematically evaluate influenza vaccine effectiveness at reducing healthcare utilization in older adults, defined as the reduction of outpatient visits, ILI and influenza hospitalizations, utilization of antibiotics and cardiovascular events by vaccination status during the influenza season., Methods: We searched MEDLINE, EMBASE, CINAHL, Cochrane Library and considered any seasonal influenza vaccine, excluding the pandemic (2009-10 season) vaccine. Reviewers independently assessed data extraction and quality assessment., Results: Of the 8308 citations retrieved, 22 studies were included in the systematic review. Overall, two studies (9%) were deemed at moderate risk of bias, thirteen (59%) at serious risk of bias and seven (32%) at critical risk of bias. For outpatient visits, we found modest evidence of protection by the influenza vaccine. For all-cause hospitalization outcomes, we found a wide range of results, mostly deemed at serious risk of bias. The included studies suggested that the vaccine may protect older adults against influenza hospitalizations and cardiovascular events. No article meeting our inclusion criteria explored the use of antibiotics and ILI hospitalizations. The high heterogeneity between studies hindered the aggregation of data into a meta-analysis., Conclusion: The variability between studies prevented us from drawing a clear conclusion on the effectiveness of the influenza vaccine on healthcare utilization in older adults. Overall, the data suggests that the vaccine may result in a reduction of healthcare utilization in the older population. Further studies of higher quality are necessary., (Copyright © 2019 The Author(s). Published by Elsevier Ltd.. All rights reserved.)