Systematic review and meta-analysis concerning the efficacy and effectiveness of seasonal influenza vaccines – (part 2)Archived

Osterholm MT, Kelley NS, Sommer A, et al. Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis The Lancet Infectious Diseases, Early Online Publication, 26 October 2011

There are several factors that can influence vaccine efficacy and effectiveness estimation. To try to avoid them, the authors have used particularly restrictive study inclusion criteria to minimise bias and confounding, and excluded randomised controlled trials in which the comparison group did not receive either placebo or a vaccine other than influenza. The results show that evidence for consistent high-level protection is elusive and there are still important knowledge gaps that should be filled in to better inform vaccination policies. In particular vaccine effectiveness studies should be systematically implemented in order to assess the real impact of vaccination programmes in relation to the different match between vaccine antigens and circulating strains during different seasons. Having said all that, and noting that it is important not to overstate the effectiveness of influenza, ECDC points out that the regular seasonal influenza vaccine remains the singly most effective way of protecting individuals against actual influenza.