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Live attenuated influenza vaccine (LAIV) is approved for eligible children 2–17 years of age. Nine randomized controlled clinical trials in children have evaluated efficacy of LAIV against culture-confirmed influenza compared with placebo or trivalent inactivated influenza vaccine (TIV). However, these data have not been collectively analyzed for children 2–17 years.
Objective:
To evaluate the efficacy of LAIV in children 2–17 years, using data from all available randomized clinical trials
Methods:
The meta-analysis was conducted using a fixed effects model. A log binomial model calculated LAIV relative risk adjusting for study variation. Because classification of drifted influenza B viruses varied, B cases were analyzed as originally classified and secondarily with all antigenic variants classified as dissimilar.
Results:
The meta-analysis included 5 placebo-controlled trials (4 were 2-season trials) and 3 single-season TIV-controlled trials in different age groups conducted between 1996–2005. Compared with placebo, the efficacy of 2 doses of LAIV in previously unvaccinated children in year 1 was 83% (95% CI: 78,87) against antigenically similar strains; 87% (95% CI: 78, 93), 86% (95% CI: 79, 91), and 76% (95% CI: 63, 84) for A/H1N1, A/H3N2, and B, respectively. With drifted B strains classified as dissimilar, efficacy against similar B strains was 93% (95% CI: 83, 97) and overall efficacy against all similar strains was 87% (95% CI: 83, 91). Year 2 efficacy compared with placebo was 87% (95% CI: 82, 91) against similar strains. Compared with TIV overall, LAIV recipients had 44% (95% CI: 28, 56) and 48% (95% CI: 38, 57) fewer cases of influenza illness caused by similar strains and all strains regardless of match, respectively.
Conclusions:
This meta-analysis provides precise estimates of LAIV efficacy among children 2–17 years, the age group for whom the vaccine is approved for use.
Sponsored by MedImmune, LLC.