RESUMO
BACKGROUND: A quadrivalent split-virion inactivated influenza vaccine (VaxigripTetra™, Sanofi Pasteur; IIV4) containing two A strains (H1N1 and H3N2) and B strains from both lineages (Victoria and Yamagata) was approved in Europe in 2016 for individuals agedâ¯≥â¯3â¯years. This study examined the efficacy and safety of IIV4 in children aged 6-35â¯months. METHODS: This was a phase III randomised controlled trial conducted in Latin America, Asia, Africa, and Europe during the Northern Hemisphere 2014/2015 and 2015/2016 and Southern Hemisphere 2014 and 2015 influenza seasons. Healthy children aged 6-35â¯months not previously vaccinated against influenza were randomised to receive two full doses 28â¯days apart of IIV4, placebo, the licensed trivalent split-virion inactivated vaccine (IIV3), an investigational IIV3 containing a B strain from the alternate lineage. The primary objective was to demonstrate efficacy against influenza illness caused by any strain or vaccine-similar strains. RESULTS: The study enrolled 5806 participants. Efficacy, assessed in 4980 participants completing the study according to protocol, was demonstrated for IIV4. Vaccine efficacy was 50.98% (97% CI, 37.36-61.86%) against influenza caused by any A or B type and 68.40% (97% CI, 47.07-81.92%) against influenza caused by vaccine-like strains. Safety profiles were similar for IIV4, placebo, and the IIV3s, although injection-site reactions were slightly more frequent for IIV4 than placebo. CONCLUSIONS: IIV4 was safe and effective for protecting children aged 6-35â¯months against influenza illness caused by vaccine-similar or any circulating strains. CLINICAL TRIAL REGISTRATION: EudraCT no. 2013-001231-51.