Patient movement across 5 community vaccination clinics in Allegheny County, May–September 2025. Each ribbon connects a patient's first clinic to their next, sized by the number of patients making that transition.
Of the 194 patients that visited more than one clinic, 91% attended the very next monthly event — regardless of where it was held. The largest single flow was 63 patients from Wilkinsburg (July 11) to Mt. Oliver (August 8). Only 18 patients (9%) skipped a month or more. This suggests booster access is driven by timing, not location preference.