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Vaccine effectiveness of the first dose of ChAdOx1 nCoV-19 and BNT162b2 against SARS-CoV-2 infection in residents of long-term care facilities in England (VIVALDI): a prospective cohort study.
Shrotri, Madhumita; Krutikov, Maria; Palmer, Tom; Giddings, Rebecca; Azmi, Borscha; Subbarao, Sathyavani; Fuller, Christopher; Irwin-Singer, Aidan; Davies, Daniel; Tut, Gokhan; Lopez Bernal, Jamie; Moss, Paul; Hayward, Andrew; Copas, Andrew; Shallcross, Laura.
  • Shrotri M; UCL Institute of Health Informatics, UCL, London, UK; Public Health England, London, UK.
  • Krutikov M; UCL Institute of Health Informatics, UCL, London, UK.
  • Palmer T; UCL Institute for Global Health, UCL, London, UK.
  • Giddings R; UCL Institute of Health Informatics, UCL, London, UK.
  • Azmi B; UCL Institute of Health Informatics, UCL, London, UK.
  • Subbarao S; Public Health England, London, UK.
  • Fuller C; UCL Institute of Health Informatics, UCL, London, UK.
  • Irwin-Singer A; Department of Health and Social Care, London, UK.
  • Davies D; Palantir Technologies UK, London, UK.
  • Tut G; Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, UK.
  • Lopez Bernal J; Public Health England, London, UK.
  • Moss P; Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, UK.
  • Hayward A; UCL Institute of Epidemiology & Healthcare, UCL, London, UK; Health Data Research UK, London, UK.
  • Copas A; UCL Institute for Global Health, UCL, London, UK.
  • Shallcross L; UCL Institute of Health Informatics, UCL, London, UK. Electronic address: l.shallcross@ucl.ac.uk.
Lancet Infect Dis ; 21(11): 1529-1538, 2021 11.
Article in English | MEDLINE | ID: covidwho-1281643
ABSTRACT

BACKGROUND:

The effectiveness of SARS-CoV-2 vaccines in older adults living in long-term care facilities is uncertain. We investigated the protective effect of the first dose of the Oxford-AstraZeneca non-replicating viral-vectored vaccine (ChAdOx1 nCoV-19; AZD1222) and the Pfizer-BioNTech mRNA-based vaccine (BNT162b2) in residents of long-term care facilities in terms of PCR-confirmed SARS-CoV-2 infection over time since vaccination.

METHODS:

The VIVALDI study is a prospective cohort study that commenced recruitment on June 11, 2020, to investigate SARS-CoV-2 transmission, infection outcomes, and immunity in residents and staff in long-term care facilities in England that provide residential or nursing care for adults aged 65 years and older. In this cohort study, we included long-term care facility residents undergoing routine asymptomatic SARS-CoV-2 testing between Dec 8, 2020 (the date the vaccine was first deployed in a long-term care facility), and March 15, 2021, using national testing data linked within the COVID-19 Datastore. Using Cox proportional hazards regression, we estimated the relative hazard of PCR-positive infection at 0-6 days, 7-13 days, 14-20 days, 21-27 days, 28-34 days, 35-48 days, and 49 days and beyond after vaccination, comparing unvaccinated and vaccinated person-time from the same cohort of residents, adjusting for age, sex, previous infection, local SARS-CoV-2 incidence, long-term care facility bed capacity, and clustering by long-term care facility. We also compared mean PCR cycle threshold (Ct) values for positive swabs obtained before and after vaccination. The study is registered with ISRCTN, number 14447421.

FINDINGS:

10 412 care home residents aged 65 years and older from 310 LTCFs were included in this analysis. The median participant age was 86 years (IQR 80-91), 7247 (69·6%) of 10 412 residents were female, and 1155 residents (11·1%) had evidence of previous SARS-CoV-2 infection. 9160 (88·0%) residents received at least one vaccine dose, of whom 6138 (67·0%) received ChAdOx1 and 3022 (33·0%) received BNT162b2. Between Dec 8, 2020, and March 15, 2021, there were 36 352 PCR results in 670 628 person-days, and 1335 PCR-positive infections (713 in unvaccinated residents and 612 in vaccinated residents) were included. Adjusted hazard ratios (HRs) for PCR-positive infection relative to unvaccinated residents declined from 28 days after the first vaccine dose to 0·44 (95% CI 0·24-0·81) at 28-34 days and 0·38 (0·19-0·77) at 35-48 days. Similar effect sizes were seen for ChAdOx1 (adjusted HR 0·32, 95% CI 0·15-0·66) and BNT162b2 (0·35, 0·17-0·71) vaccines at 35-48 days. Mean PCR Ct values were higher for infections that occurred at least 28 days after vaccination than for those occurring before vaccination (31·3 [SD 8·7] in 107 PCR-positive tests vs 26·6 [6·6] in 552 PCR-positive tests; p<0·0001).

INTERPRETATION:

Single-dose vaccination with BNT162b2 and ChAdOx1 vaccines provides substantial protection against infection in older adults from 4-7 weeks after vaccination and might reduce SARS-CoV-2 transmission. However, the risk of infection is not eliminated, highlighting the ongoing need for non-pharmaceutical interventions to prevent transmission in long-term care facilities.

FUNDING:

UK Government Department of Health and Social Care.
Subject(s)

Full text: Available Collection: International databases Database: MEDLINE Document Type: Article Main subject: Immunogenicity, Vaccine / COVID-19 Vaccines / COVID-19 / Nursing Homes Subject: Immunogenicity, Vaccine / COVID-19 Vaccines / COVID-19 / Nursing Homes Type of study: Diagnostic study / Etiology study / Incidence study / Observational study / Prognostic study / Risk factors Language: English Journal: Lancet Infect Dis Clinical aspect: Etiology / Prognosis Year: 2021

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Full text: Available Collection: International databases Database: MEDLINE Document Type: Article Main subject: Immunogenicity, Vaccine / COVID-19 Vaccines / COVID-19 / Nursing Homes Subject: Immunogenicity, Vaccine / COVID-19 Vaccines / COVID-19 / Nursing Homes Type of study: Diagnostic study / Etiology study / Incidence study / Observational study / Prognostic study / Risk factors Language: English Journal: Lancet Infect Dis Clinical aspect: Etiology / Prognosis Year: 2021
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