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Vaccine Effectiveness Against Infection and Death Due to SARS-CoV-2, Following One and Two Doses of the BNT162b2 and ChADox-1 in Residents of Long-Term Care Facilities in England, Using a Time-Varying Proportional Hazards Model
30 Pages Posted: 13 Sep 2021
More...Abstract
Background: We investigated the effect of both doses of either BNT162b2 or ChAdOx-1 vaccine among residents of Long-term care facilities (LTCFs) in England. This cohort is at particularly high risk for severe outcomes related to COVID-19 and is regularly tested regardless of symptoms.
Methods: This observational study uses testing, immunisation and mortality data from 8 December 2020 to 25 June 2021 in LTCF residents aged 65 years and above. Cox proportional hazards models were used to derive adjusted hazard ratios (aHR) for the risk of infection and death within 28 days of positive test result, adjusted for sex, age-group, previous infection, deprivation, and incidence rate in the local authority area. The impact of interval between first and second dose was also explored.
Findings: Of 219733 LTCF residents, 41828 (19%) had a positive test and 10719 (4.9%) died within 28 days of a positive test during the study period. Relative to unvaccinated individuals, aHR for infection were lowest at 0.43 (95% CI 0.35-0.52) 36-49 days after first dose and 0.27 (0.20-0.38) at 29-60 days following second dose . Against death, aHR was lowest at 0.25 (0.20-0.31) 28-56 days after first dose and 0.13 (0-05-0.32) in the 1-14 days after second dose. As expected, some waning of protection against infection was observed after seven weeks from first dose which persisted to 2-4 weeks following second dose.
Interpretation: Vaccination with one dose of BNT162b2 and ChAdOx-1 provides moderate protection against infection and death in residents in LTCFs. Protection is strong after two doses.
Funding: None to declare.
Declaration of Interest: None to declare.
Ethical Approval: Vaccine effectiveness studies are undertaken by Public Health England as part of ongoing surveillance activities and did not require ethical approval.
Keywords: COVID-19, SARS-CoV-2, long term care facilities, elderly, care homes, immunosenescence.
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