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In health individuals (patients), do influenza vaccines (intervention) decrease the risk of laboratory-confirmed influenza virus infection (outcomes)?
Studies were selected which compared influenza risk between vaccinated versus non-vaccinated individuals. Both inactivated (trivalent inactivated vaccines – TIV) and live attenuated (LAIV) vaccines were included. Efficacy was studied by selecting randomised placebo-controlled trials (RCTs). Effectiveness was studied by selecting observational studies. Primary outcome in both cases was influenza infection confirmed by RT-PCR or culture. Studies that used serology as an endpoint and vaccine challenge studies were excluded.
MEDLINE was searched for English-only studies that included efficacy or effectiveness data against all circulating influenza viruses during individual seasons. Risk of bias of included studies was not assessed.
Seventeen RCTs and 14 observational trials were included. One TIV RCT included children aged 6–24 months over two seasons. Its efficacy was 66% the first year, and −7% the next year. Six LAIV RCTs included …
Correspondence to Emma Hulbert-Powell, Department of Child Health, Salisbury District Hospital, Salisbury SP2 8BJ, UK;
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