@article{b630eda4e02a4d35be3cb571b7be45ef,
title = "Challenges in estimating the effectiveness of 2 doses of Covid-19 vaccine beyond 6 months in England",
abstract = "Understanding how the effectiveness of coronavirus disease 2019 (COVID-19) vaccine changes over time and in response to new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants is crucial to scheduling subsequent doses. In a previous study, Horne et al. (1) quantified vaccine effectiveness (VE) over 6 consecutive 4-week periods from 2 weeks to 26 weeks after the second dose. Waning of hazard ratios (HRs) when comparing vaccinated persons with unvaccinated persons was approximately log-linear over time and was consistent across COVID-19– related outcomes and risk-based subgroups. To investigate waning beyond 26 weeks and in the era of the Omicron variant, we extended follow-up to the earliest of 50 weeks after the second dose or March 31, 2022.",
author = "Horne, \{Elsie M.F.\} and Hulme, \{William J.\} and Keogh, \{Ruth H.\} and Palmer, \{Tom M.\} and Williamson, \{Elizabeth J.\} and Parker, \{Edward P.K.\} and Walker, \{Venexia M.\} and Rochelle Knight and Yinghui Wei and Kurt Taylor and Louis Fisher and Jessica Morley and Amir Mehrkar and Iain Dillingham and Sebastian Bacon and Ben Goldacre and Sterne, \{Jonathan A.C.\}",
year = "2023",
month = sep,
day = "1",
doi = "10.1093/aje/kwad179",
language = "English",
volume = "0",
journal = "American Journal of Epidemiology",
issn = "0002-9262",
publisher = "Oxford University Press",
number = "0",
}