Trivalent inactivated influenza vaccine effective against influenza A(H3N2) variant viruses in children during the 2014/15 season, Japan

Abstract

The 2014/15 influenza season in Japan was characterised by predominant influenza A(H3N2) activity; 99% of influenza A viruses detected were A(H3N2). Subclade 3C.2a viruses were the major epidemic A(H3N2) viruses, and were genetically distinct from A/New York/39/2012(H3N2) of 2014/15 vaccine strain in Japan, which was classified as clade 3C.1. We assessed vaccine effectiveness (VE) of inactivated influenza vaccine (IIV) in children aged 6 months to 15 years by test-negative case–control design based on influenza rapid diagnostic test. Between November 2014 and March 2015, a total of 3,752 children were enrolled: 1,633 tested positive for influenza A and 42 for influenza B, and 2,077 tested negative. Adjusted VE was 38% (95% confidence intervals (CI): 28 to 46) against influenza virus infection overall, 37% (95% CI: 27 to 45) against influenza A, and 47% (95% CI: -2 to 73) against influenza B. However, IIV was not statistically significantly effective against influenza A in infants aged 6 to 11 months or adolescents aged 13 to 15 years. VE in preventing hospitalisation for influenza A infection was 55% (95% CI: 42 to 64). Trivalent IIV that included A/New York/39/2012(H3N2) was effective against drifted influenza A(H3N2) virus, although vaccine mismatch resulted in low VE.

School‐based surveillance for influenza vaccine effectiveness during 2014‐2015 seasons in Hong Kong

“…However, both this and our studies were limited by small sample size in each age group which led to wide 95% confidence intervals and significant overlap of the VE estimates. Similar findings were observed in a study of 2368 inpatients in Beijing in the 2014‐2015 season, a Japanese surveillance in 2013‐2014, and two US studies in 2013‐2014 and 2014‐2015 seasons. Our finding supported possible impact of extending the influenza vaccination programs to school‐age children, but further studies are needed to address the cost‐effectiveness of this vaccination strategy.…”

Clinical characteristics of influenza virus-induced lower respiratory infection during the 2015 to 2016 season

“…Although our study was not designed to demonstrate the effectiveness of the influenza vaccine, previous reports have shown a vaccine efficacy rate of 61%e63% against A(H1N1)pdm09 and prevention of hospitalization in 76% of cases [8,23]. The rate of immunization was four in 21 (19%) in the admitted patients and one in six (17%) in PB, which was lower than the general immunization rate of 50% in Japan [24]. Thus, our findings support the current recommendations to vaccinate children.…”

The safety and efficacy of quadrivalent live attenuated influenza vaccine in Japanese children aged 2‐18 years: Results of two phase 3 studies

“…In the UK effectiveness study from the same season, the inactivated influenza vaccine did not appear to be effective against H3N2 strains among children under 18 years of age (efficacy estimate of −73.2%, 95% CI: −456.9, 46.2) . A similar test‐negative outpatient study conducted during the 2014‐2015 season in Japan in children 6 months through 15 years of age yielded an effectiveness estimate of 37% (95% CI: 27, 45) for the trivalent inactivated vaccine against influenza A strains …”