This publication corresponds to the study protocol of the Baseline Use Case proposed in T.5.2 (WP5) in the BY-COVID project on “SARS-CoV-2 Vaccine effectiveness in preventing SARS-CoV-2 infection.” Research question: We aim to investigate the real-world effectiveness of SARS-CoV-2 primary vaccination as compared to partial or no vaccination in preventing SARS-CoV-2 infection in virtually all resident populations spanning different countries. Study design: An observational retrospective longitudinal (cohort) study using routinely collected social, health and care data from several countries/regions in Europe. We have designed the observational study to emulate a hypothetical Target Trial (TT) of the causal effect of SARS-CoV-2 vaccination programs in preventing SARS-CoV-2 infections. File included in this publication: Study protocol (PDF): The protocol provides a work plan, including details on the research team, study rationale, methodology, and ethical aspects. The implementation of this study is supported by supplementary documents including a causal model (DAG), a common data model specification, and a simulated dataset following the specification of the common data model. This information is available at https://doi.org/10.5281/zenodo.6913045.

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