Effectiveness of mRNA COVID-19 Vaccines as First Booster Doses in England: An Observational Study in OpenSAFELY-TPP - Horne, EMF; Hulme, WJ; Parker, EPK; Keogh, RH; Williamson, EJ; Walker, VM; Palmer, TM; Denholm, R; Knight, R; Curtis, HJ; Walker, AJ; Andrews, CD; et al. (Epidemiology, 2024)