Efficacy and safety of a live attenuated influenza vaccine in Chinese healthy children aged 3–17 years in one study center of a randomized, double-blind, placebo-controlled phase 3 clinical trial, 2016/17 season

No data on the safety and efficacy of a live attenuated influenza vaccine in China have ever been reported. At a site of a phase 3 randomized, double-blind, placebo-controlled clinical trial in eastern China, eligible healthy children aged 3–17 years underwent randomization to receive live attenuated vaccine or placebo at a ratio of 1:1. The primary objective of the study was the prevention of laboratory-confirmed influenza illness during the surveillance period, starting on day 15 after vaccination. A total of 2000 participants were enrolled, with 998 receiving the vaccine and 1001 receiving placebo. Sixty-four cases of influenza-like illness were observed, of which, 44 were laboratory-confirmed (12 in vaccine group versus 32 in placebo group). Vaccine efficacy was 62.5% (95%CI: 27.6–80.6) against all types of influenza and 63.3% (95%CI: 27.5–81.5) against influenza H3N2 illness. 11 severe adverse events reported (7 in LAIV group versus 4 in placebo group) were all deemed to be non-vaccine-related. Adverse events occurred in 412 (41.3%) participants in the vaccine group versus 389 (38.9%; p = 0.274) participants in the placebo group. Significant increase incidence of fever was observed in participants in the vaccine group, especially in those aged 3–9 years. The live attenuated influenza vaccine showed good efficacy and safety among 3- to 17-year-olds children during the 2016–2017 season at a site in eastern China. Clinical Trial Registry Number: NCT02964065.