The Risk of Bias in Vaccine Effectiveness (RoB-VE) project:introduction to a methodological initiative to improve risk-of-bias assessment and reporting in vaccine effectiveness research

BACKGROUND AND OBJECTIVE: Vaccine effectiveness (VE) studies are essential for informing immunization policy and public health decision-making. However, the observational nature of most VE studies introduces unique methodological challenges, including biases that are not adequately addressed by existing risk-of-bias (RoB) tools. The Risk of Bias in Vaccine Effectiveness (RoB-VE) project is an international, multiphase methodological research initiative aimed at improving the quality, transparency, interpretability, and reporting of VE research. DISCUSSION: Funded by the Canadian Institutes of Health Research and supported by many global partners, the project seeks to generate a comprehensive toolkit for VE studies. This includes an RoB assessment resource tailored to VE study designs and a complementary reporting guideline to enhance consistency in VE study reporting. The project follows an evidence-informed approach, beginning with a review of the literature to inform tool development, and progressing through interest holder engagement, modified Delphi consensus, usability testing, and beta validation. This introductory paper outlines the rationale, scope, and methodology of the RoB-VE project. These efforts aim to strengthen the methodological foundation of VE research and support more reliable evidence synthesis and policy development. PLAIN LANGUAGE SUMMARY: VE studies measure how well vaccines work in real-world scenarios. These studies are essential for shaping vaccination recommendations. To assess the validity of VE studies, it is necessary to carry out an RoB assessment, which involves looking at different aspects of the study (eg, data collection methods, how participants are recruited, etc.) that have the potential to yield misleading results. Existing RoB assessment tools do not fully capture issues particularly relevant to VE studies and inconsistent reporting limits their usefulness. To address this, we are conducting the RoB-VE project. This project aims to improve the quality, transparency, interpretability, and reporting of VE research through the development, validation, and dissemination of a robust and user-friendly RoB assessment tool, specifically tailored for assessing VE studies. Our methodology involves a comprehensive multistep process based on established approaches. A broad range of international participants with diverse expertise and profiles will be engaged along the way to refine and finalize the tool. After pilot testing the beta version of the tool and making further refinements, we aim to deliver version 1 of the tool, which will undergo a large-scale application phase to assess its reliability and usefulness. Additionally, we will develop a reporting guideline to enhance the completeness of reporting of VE studies. This introductory paper outlines the rationale, scope, and methodology of the RoB-VE project. This project will elevate the standards of evidence synthesis, ultimately contributing to more reliable, transparent, and impactful research in the critical field of VE evaluation.