Effectiveness of mRNA BNT162b2 COVID-19 vaccine up to 6 months in a large integrated health system in the USA: a retrospective cohort study

Sara Y. Tartof, Jeff M. Slezak, Heidi Fischer, Vennis Hong, Bradley K. Ackerson, Omesh N. Ranasinghe, Timothy B. Frankland, Oluwaseye A. Ogun,
Joann M. Zamparo, Sharon Gray, Srinivas R. Valluri, Kaije Pan, Frederick J. Angulo, Luis Jodar, and John M. McLaughlin