The level of evidence is downgraded by imprecise results (small number of included studies in each comparison).
A Cochrane review «Vaccines for preventing influenza in healthy children»1 «Jefferson T, Rivetti A, Di Pietrantonj C et al. Vaccines for preventing influenza in healthy children. Cochrane Database Syst Rev 2012;(8):CD004879. »1 included 75 studies with about 300 000 subjects.
In 7 RCT:s, live attenuated vaccines showed 80% overall efficacy (RR 0.20; 95% CI 0.13 to 0.32) for children of all age groups. The RD (risk difference) for children under the age of 6 was -0.15 (95% CI -0.20 to -0.10); which means that seven children had to be vaccinated to avoid one case of influenza (NNV=7). The overall RD for those aged 2 to 16 years was -0.16 (95% CI -0.20 to -0.11); NNV = 6. No usable age-specific data for those aged two or less was found.
In 5 RCT:s, inactivated vaccines showed lower efficacy (VE = 59%) (RR 0.41; 95% CI 0.29 to 0.59) than live attenuated vaccines. The RD for those aged six or older was -0.35 (95% CI -0.54 to -0.15); NNV = 28.