Promises and pitfalls of meta-analysis in vaccine research

Meta-analysis continues to grow in usage despite increased concern regarding its soundness. Over twenty meta-analyses directly pertain to vaccines. Vaccine researchers need to understand the technique as well as the criticisms. Meta-analysis involves four steps. First, the meta-analyst should establish certain criteria in advance of the second step where the meta-analyst gathers the data--the results of the individual studies. Third, the meta-analyst assesses the individual studies for combinability and, fourth, the meta-analyst actually combines the data to generate conclusions. Vaccine meta-analyses have addressed a variety of vaccines and a variety of study objectives including efficacy, immunogenicity and safety. Three classical concerns revolve around the issue of publication bias, data dredging and individual study variability. Additionally, vaccine meta-analyses suffer concerns particular to the field of vaccine research.