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.