Generic protocols for retrospective case-control studies and retrospective cohort studies to assess the effectiveness of rotavirus vaccination in EU Member States based on computerised databases were published by the European Centre for Disease Prevention and Control (ECDC). They describe the information that should be collected by country and region in vaccine effectiveness studies and the data sources that may be available to identify virus-related outcomes a vaccine is intended to avert, including hospital registers, computerised primary care databases, specific surveillance systems (i.e. laboratory surveillance, hospital surveillance, primary care surveillance) and laboratory registers. Based on a meta-analysis comprising 49 cohort studies and 10 case-control studies, Efficacy and effectiveness of influenza vaccines in elderly people: a systematic review (Lancet 2005;366(9492):1165-74) highlights the heterogeneity of outcomes and study populations included in such studies and the high likelihood of selection bias.
Non-specific effects of vaccines, such as a decrease of mortality, have been claimed in observational studies but generally result from bias and confounding. Data collection in observational studies (Trop Med Int Health 2009;14(9):969-76.) and Methodological issues in the design and analysis of cohort studies (Trop Med Int Health 2009;14(9):977-85) provide recommendations for vaccine observational studies conducted in countries with high mortality; these recommendations have wider relevance.
|Annex 1.||Guidance on conducting systematic revies and meta-analyses of completed comparative pharmacoepidemiological studies of safety outcomes|