Abstract
The estimand framework as outlined in ICH E9(R1) has been extensively discussed and implemented in clinical trials of therapeutic products. However, there is limited literature on the application of the framework in preventive vaccine trials, which has many unique characteristics, including emphasis on estimating the per-protocol or "biological" effect. We provide a comprehensive review of the application of the framework to preventive vaccine trials evaluating clinical outcome and immunogenicity, focusing on commonly encountered intercurrent events including but not limited to: noncompliance with vaccination schedule and blood sampling window, infection not meeting protocol definition, death, and use of prohibited products. We discuss various considerations in choosing strategies to handle intercurrent events in terms of their utility in addressing the scientific questions. Finally, we provide considerations and examples for summarizing study estimands and data handling which may be incorporated into the protocol and statistical analysis plan.