Influenza vaccine efficacy in young children attending childcare: A randomised controlled trial

Aim Influenza causes a substantial burden in young children. Vaccine efficacy ( VE ) data are limited in this age group. We examined trivalent influenza vaccine ( TIV ) efficacy and safety in young children attending childcare. Methods A double‐blind, randomised controlled trial in children aged 6 to <48 months was conducted with recruitment from Sydney childcare centres in 2011. Children were randomised to receive two doses of TIV or control hepatitis A vaccine. Efficacy was evaluated against polymerase chain reaction‐confirmed influenza using parent‐collected nose/throat swabs during influenza‐like‐illness. Safety outcomes were assessed during 6 months of follow‐up. Results Fifty‐seven children were allocated to influenza vaccine and 67 to control; all completed the study. The influenza attack rate was 1.8 vs 13.4% in the TIV and control groups, respectively; VE 87% (95% CI : 0–98%). For children aged 24 to <48 months, 0 vs 8 (18.6%) influenza infections occurred in the TIV and control groups respectively, giving a VE of 100% (16–100%). Efficacy was not shown in children 6 to <24 months, probably due to insufficient power. Injection site and systemic adverse events were mostly mild to moderate with no significant differences, apart from more mild diarrhoea following dose 2 in TIV recipients (11.8 vs 0%). Conclusions Influenza vaccine appeared efficacious in the subgroup of children aged 24 to <48 months, although caution is required due to the small number of participants. There were no serious adverse events and most parents would vaccinate again. Influenza vaccination in a childcare setting could be valuable and a larger confirmatory study would be helpful.