Comparative effectiveness of ChAdOx1 versus BNT162b2 COVID-19 vaccines in Health and Social Care workers in England: a cohort study using OpenSAFELYHulme WJ, Williamson EJ, Green A, Bhaskaran K, McDonald HI, Rentsch CT, Schultze A, Tazare J, Curtis HJ, Walker AJ, Tomlinson L, Palmer T, Horne E, MacKenna B, Morton CE, Mehrkar A, Fisher L, Bacon S, Evans D, Inglesby P, Hickman G, Davy S, Ward T, Croker R, Eggo RM, Wong AY, Mathur R, Wing K, Forbes H, Grint D, Douglas IJ, Evans SJ, Smeeth L, Bates C, Cockburn J, Parry J, Hester F, Harper S, Sterne JA, Hernán M, Goldacre B.