The most effective technique of avoiding influenza virus infection is influenza vaccination. The prevalence of influenza among students is greater than in other age groups. The efficacy of seasonal inactivated influenza vaccine (IIV) in a community population of schoolchildren was assessed in this study across two seasons. The data for this study came from a cross-sectional survey of public pupils conducted in the 2012/2013 and 2014/2015 school years. The questionnaire was sent to all public pupils in a survey region of the desired grade level, and 7945 respondents were included in the analysis. The vaccination status and the onset of influenza were determined using a self-reported questionnaire. To account for clustering within schools and individual variables, and to construct odds ratios (ORs) and 95 percent confidence intervals (CIs) for associations between vaccination status and influenza onset, generalized linear mixed models were employed. The incidence of influenza was greater in 2015 than in 2013, while vaccination rates were comparable between the two seasons. In both the 2013 and 2015 studies, receiving a one- or two-dose vaccine was more protective against influenza than not being vaccinated. In both the 2013 and 2015 studies, full immunization was likewise more protective.

In a community-based real-world environment, seasonal IIV proved protective against influenza in Japanese kids. The variation in clinical efficacy of IIV across seasons was most likely caused by an antigenic mismatch between circulating and vaccination strains.