Fairall, L. (2025) “Real-world effectiveness of Ad26.COV2.S or BNT162b2 booster vaccines against severe COVID-19 in adults who received a primary dose of Ad26.COV2.S in South Africa during the Delta period: A retrospective cohort study using medical scheme data”, South African Medical Journal, 115(7), p. e2532 . doi:10.7196/SAMJ.2025.v115i7.2532.