Conducting reliable observational vaccine effectiveness studies is highly important, particularly in epidemics or outbreaks. These studies are essential for making informed program and policy decisions based on solid evidence. The consultation aims to highlight key considerations in vaccine effectiveness research, including discussions on best practices and standards. It will involve epidemiological and statistical experts who will delve into various aspects of study design and analysis. These aspects include identifying potential sources of bias, strategies for mitigating bias, and the importance of transparent reporting and synthesis of research findings.