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

BACKGROUND: Quadrivalent live attenuated influenza vaccine (Q/LAIV) has not been assessed in Japanese children.

OBJECTIVES: Evaluate safety and efficacy of Q/LAIV in Japanese children.

PATIENTS/METHODS: Two phase 3 studies were conducted in the 2014-2015 influenza season. Study 1 was an open-label, uncontrolled single arm, multicenter study of Q/LAIV safety in subjects aged 2-6 years. Study 2 was a randomized, double-blind, placebo-controlled multicenter study of Q/LAIV safety and efficacy; subjects aged 7-18 years were randomized 2:1 to receive Q/LAIV or placebo. Primary efficacy endpoint was laboratory-confirmed symptomatic influenza infection caused by vaccine-matched strains; secondary endpoint evaluated efficacy against all strains regardless of match. Both studies reported solicited symptoms, adverse events (AEs), and serious AEs.

RESULTS: In Study 1, 100 subjects received Q/LAIV. In Study 2, 1301 subjects received Q/LAIV (n = 868) or placebo (n = 433). Treatment-emergent AEs occurred in 42% of subjects in Study 1, and in 24.3% of subjects in the Q/LAIV arm and in 25.9% of subjects in the placebo arm in Study 2. In Study 2, a single infection by a vaccine-matched strain was reported in the placebo arm, resulting in a vaccine efficacy estimate of 100% (95% CI: -1875.3, 100.0); efficacy for all strains regardless of match to the vaccine was 27.5% (95% CI: 7.4, 43.0).

CONCLUSIONS: Quadrivalent live attenuated influenza vaccine did not meet its primary efficacy endpoint as only a single infection by a vaccine-matched strain was detected; however, efficacy for the secondary endpoint, all strains regardless of match, was achieved. Q/LAIV was generally well tolerated in the Japanese pediatric population.