Table 1.

Self‐controlled case series vs. self‐controlled risk interval

	Self‐controlled case series (SCCS)	Self‐controlled risk interval (SCRI)
Typical uses	Safety of drugs or vaccines on acute‐onset outcomes	Mainly used to study safety of vaccines on acute‐onset outcomes
Who’s included	Cases. Patients with the outcome during the study period. Never‐treated patients can be included to contribute to the estimation of time‐varying confounder effects	Exposed cases. Patients with the outcome and the exposure during the study period.
Study period	Typically calendar year(s)	Time immediately surrounding an exposure event.
Design	Incidence during risk interval compared to that during baseline time. All time that isn’t part of a risk interval (or a pre‐risk or washout interval, if used) is included as baseline time.	Incidence during risk interval compared to that during control interval. Control interval is typically short.
Advantage	Greater power than SCRI. All time outside risk periods (and washout + pre‐risk periods) is used as baseline time	Less susceptible to time‐varying confounding than SCCS
Disadvantage	More susceptible to time‐varying confounding than SCRI due to longer study period. Must be handled through adjustment.	Less power than SCCS

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