Study design · Planning

Self-Controlled Case Series (SCCS) Design Diagram

The self-controlled case series drawn in the Schneeweiss/Gatto convention — assessment, exposure, and follow-up windows anchored on a timeline so the design's temporal logic is explicit.

Download SVG Open code and full worked example

When to use it

For acute events and transient exposures (classically vaccine safety). Only cases are needed; each person's exposed (risk) time is compared with their own unexposed (baseline) time over an observation period.

How to read it

The observation period is split into a post-exposure risk window and baseline time; events are counted in each, and the incidence-rate ratio compares risk vs baseline WITHIN each person — controlling all time-fixed confounders.

Worked example

A single case's 365-day observation period contains an exposure starting day 60, a post-exposure risk window, and baseline time; events are tallied in risk vs baseline windows.

Windows: observation [0, 365], exposure [60, 90], risk window [60, 120], baseline = remaining time; events marked across the observation lane.

Result: The within-person comparison of risk-window vs baseline event rate eliminates time-fixed confounding; the diagram also flags that age/seasonal time-varying confounders must be modeled, since the design does not self-match those.

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Self-controlled case series (SCCS)

Reference: Schneeweiss S, Rassen JA, Brown JS, et al. Graphical Depiction of Longitudinal Study Designs in Health Care Databases. Ann Intern Med. 2019;170(6):398-406.