Keywords: Vaccines, Group Sequential
Designing studies for confirmation of efficacy of a novel vaccine is often challenging when the disease incidence is expected to be very low, and potentially variable. One approach to mitigate the risk of misspecifying the underlying incidence of the disease is through the use of an event-driven design (by conditioning on the total number of events). Since the number of patients (and time) needed to accrue the desired number of events can be large, interim efficacy and futility assessments are often desirable and can be incorporated through the use group sequential methods. This talk will focus on statistical and operational considerations in designing group sequential vaccine efficacy studies.