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Abstract
BACKGROUND The duration and effectiveness of immunity from infection with and vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are relevant to pandemic policy interventions, including the timing of vaccine boosters. METHODS We investigated the duration and effectiveness of immunity in a prospective cohort of asymptomatic health care workers in the United Kingdom who underwent routine polymerase-chain-reaction (PCR) testing. Vaccine effectiveness (≤10 months after the first dose of vaccine) and infection-acquired immunity were assessed by comparing the time to PCR-confirmed infection in vaccinated persons with that in unvaccinated persons, stratified according to previous infection status. We used a Cox regression model with adjustment for previous SARS-CoV-2 infection status, vaccine type and dosing interval, demographic characteristics, and workplace exposure to SARS-CoV-2. RESULTS Of 35,768 participants, 27% (9488) had a previous SARS-CoV-2 infection. Vaccine coverage was high: 95% of the participants had received two doses (78% had received BNT162b2 vaccine [Pfizer–BioNTech] with a long interval between doses, 9% BNT162b2 vaccine with a short interval between doses, and 8% ChAdOx1 nCoV-19 vaccine [AstraZeneca]). Between December 7, 2020, and September 21, 2021, a total of 2747 primary infections and 210 reinfections were observed. Among previously uninfected participants who received long-interval BNT162b2 vaccine, adjusted vaccine effectiveness decreased from 85% (95% confidence interval [CI], 72 to 92) 14 to 73 days after the second dose to 51% (95% CI, 22 to 69) at a median of 201 days (interquartile range, 197 to 205) after the second dose; this effectiveness did not differ significantly between the long-interval and short-interval BNT162b2 vaccine recipients. At 14 to 73 days after the second dose, adjusted vaccine effectiveness among ChAdOx1 nCoV-19 vaccine recipients was 58% (95% CI, 23 to 77) — considerably lower than that among BNT162b2 vaccine recipients. Infection-acquired immunity waned after 1 year in unvaccinated participants but remained consistently higher than 90% in those who were subsequently vaccinated, even in persons infected more than 18 months previously. CONCLUSIONS Two doses of BNT162b2 vaccine were associated with high short-term protection against SARS-CoV-2 infection; this protection waned considerably after 6 months. Infection-acquired immunity boosted with vaccination remained high more than 1 year after infection.
Original language | English |
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Pages (from-to) | 1207-1220 |
Number of pages | 14 |
Journal | New England Journal of Medicine |
Volume | 386 |
Issue number | 13 |
Early online date | 16 Feb 2022 |
DOIs | |
Publication status | Published - 31 Mar 2022 |
Keywords
- SARS-CoV-2
- Covid-19 vaccination
- prospective studies
- adaptive immunity/immunology
- COVID-19 Nucleic Acid Testing
- humans
- BNT162 vaccine/therapeutic use
- ChAdOx1 nCoV-19/therapeutic use
- United Kingdom
- asymptomatic diseases
- COVID-19 vaccines/immunology
- COVID-19/diagnosis
- vaccination/methods
- vaccine efficacy
- health personnel
ASJC Scopus subject areas
- General Medicine
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- 1 Finished
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Impact of detectable anti-SARS-COV2 on the subsequent incidence of COVID-19 in healthcare workers
Price, L. (CoI) & Hopkins, S. (PI)
1/09/20 → 31/08/23
Project: Research Grant