Meta-analyses in vaccinology

The use of meta-analysis as a method for systematic review of the literature has grown substantially since its appearance in 1988. We obtained and reviewed 134 meta-analyses cited in Current Contents, MEDLINE, EMBASE, and the Cochrane Database of Systematic Reviews reporting original meta-analyses in human subjects regarding vaccines directed against infectious diseases and their sequelae. More than a fifth of the meta-analyses concerned influenza vaccines and almost a sixth concerned pneumococcal vaccines. Nearly 80% principally evaluated efficacy, effectiveness, and immunogenicity. We review three prominent meta-analyses to illustrate features of the methods and make several observations. These concern electronic searches, the Cochrane Collaboration, individual study heterogeneity, and individual study quality as well as the utility of meta-analyses despite the limitations and the likelihood of its endurance as a methodologic technique in vaccinology.