Abstract
SummaryBackgroundA new variant of SARS-CoV-2, B.1.1.7, emerged as the dominant cause of COVID-19 disease in the UK from November, 2020. We report a post-hoc analysis of the efficacy of the adenoviral vector vaccine, ChAdOx1 nCoV-19 (AZD1222), against this variant.MethodsVolunteers (aged ≥18 years) who were enrolled in phase 2/3 vaccine efficacy studies in the UK, and who were randomly assigned (1:1) to receive ChAdOx1 nCoV-19 or a meningococcal conjugate control (MenACWY) vaccine, provided upper airway swabs on a weekly basis and also if they developed symptoms of COVID-19 disease (a cough, a fever of 37·8°C or higher, shortness of breath, anosmia, or ageusia). Swabs were tested by nucleic acid amplification test (NAAT) for SARS-CoV-2 and positive samples were sequenced through the COVID-19 Genomics UK consortium. Neutralising antibody responses were measured using a live-virus microneutralisation assay against the B.1.1.7 lineage and a canonical non-B.1.1.7 lineage (Victoria). The efficacy analysis included symptomatic COVID-19 in seronegative participants with a NAAT positive swab more than 14 days after a second dose of vaccine. Participants were analysed according to vaccine received. Vaccine efficacy was calculated as 1 − relative risk (ChAdOx1 nCoV-19 vs MenACWY groups) derived from a robust Poisson regression model. This study is continuing and is registered with ClinicalTrials.gov, NCT04400838, and ISRCTN, 15281137.FindingsParticipants in efficacy cohorts were recruited between May 31 and Nov 13, 2020, and received booster doses between Aug 3 and Dec 30, 2020. Of 8534 participants in the primary efficacy cohort, 6636 (78%) were aged 18–55 years and 5065 (59%) were female. Between Oct 1, 2020, and Jan 14, 2021, 520 participants developed SARS-CoV-2 infection. 1466 NAAT positive nose and throat swabs were collected from these participants during the trial. Of these, 401 swabs from 311 participants were successfully sequenced. Laboratory virus neutralisation activity by vaccine-induced antibodies was lower against the B.1.1.7 variant than against the Victoria lineage (geometric mean ratio 8·9, 95% CI 7·2–11·0). Clinical vaccine efficacy against symptomatic NAAT positive infection was 70·4% (95% CI 43·6–84·5) for B.1.1.7 and 81·5% (67·9–89·4) for non-B.1.1.7 lineages.InterpretationChAdOx1 nCoV-19 showed reduced neutralisation activity against the B.1.1.7 variant compared with a non-B.1.1.7 variant in vitro, but the vaccine showed efficacy against the B.1.1.7 variant of SARS-CoV-2.FundingUK Research and Innovation, National Institute for Health Research (NIHR), Coalition for Epidemic Preparedness Innovations, NIHR Oxford Biomedical Research Centre, Thames Valley and South Midlands NIHR Clinical Research Network, and AstraZeneca.
Highlights
The COVID-19 pandemic continues to cause considerable mortality, placing a substantial burden on health-care systems around the world and having profound social and economic consequences due to the measures imple mented to control the SARS-CoV-2 virus
Between Oct 1, 2020, and Jan 14, 2021, 520 participants developed SARS-CoV-2 infection. 1466 nucleic acid amplification test (NAAT) positive nose and throat swabs were collected from these participants during the trial
Our findings show that while laboratory neutralising antibody titres generated by vaccination with ChAdOx1 nCoV-19 vaccine are lower for the B.1.1.7 lineage, clinical vaccine efficacy against symptomatic COVID-19 was observed for the B.1.1.7 variant at 70·4%, with a lower bound of 43·6% for the 95% CI
Summary
The COVID-19 pandemic continues to cause considerable mortality, placing a substantial burden on health-care systems around the world and having profound social and economic consequences due to the measures imple mented to control the SARS-CoV-2 virus. C Ludden PhD); National Infection Service, Public Health. Salisbury, UK (S Charlton PhD, B Hallis PhD); Department of Clinical Sciences, Liverpool School of Tropical Medicine and Liverpool University Hospitals. NHS Foundation Trust, Liverpool, UK (A M Collins PhD, Prof D M Ferreira PhD, H C Hill PhD); UK Biocentre, Milton Keynes, UK (T Cox PhD); Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, UK (T C Darton DPhil); Department of Infection and Tropical Medicine, Sheffield Teaching Hospitals NHS. Foundation Trust, Sheffield, UK (T C Darton); Department of Infection and Tropical.
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