Successfully carrying out the linking of databases for large scale vaccine safety studies comes with several challenges. First, the reluctance of local authorities to share data is understandable. Second, the challenges of processing data in the scale of millions, collecting data from databases in different languages, and extracting data from records not designed for international data sharing is a daunting task. Third, hidden differences in the way data is treated in different centers compromise data comparability. Fourth, the mathematical subtleties needed to adapt statistical methods to unique large-scale studies are a highly specialized knowledge. All these challenges have caused investigators to be skeptical about the potential success of an international data linkage project.

In the Brighton Collaboration, we have integrated experience gained in drug safety and in national large linked data bases investigating vaccine safety hypotheses (e.g. in the USA, Denmark). In the VAESCO project, several hurdles specific to international vaccine safety data sharing could be overcome. Based on this work, future data linkage studies will follow the following framework.

The Brighton Linkage Program follows an 11 step process: