Selecting the most informative positive and negative controls for self-controlled case series (SCCS): Rationale, approach, and lessons from studies investigating the safety of COVID-19 vaccines. - Rudan I; Katikireddi SV; Kerr S; Millington T; Grange Z; Sullivan C; Fagbamigbe AF; Swallow B; Kurdi A; Morrison K; Jeffrey K; Simpson CR; et al. (Journal of global health, 2024)