CHALLENGES IN ESTIMATING THE EFFECTIVENESS OF 2 DOSES OF COVID-19 VACCINE BEYOND 6 MONTHS IN ENGLAND.

The article discusses a study which examined the effectiveness of two doses of coronavirus disease 2019 (COVID-19) vaccine beyond six months in England. Topics include increase in the cumulative incidence of receiving a third dose of vaccine during the eight weeks following eligibility, basis of the effectiveness of two doses during later comparison periods, and important factors in interpreting estimated vaccine effectiveness (VE).