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COVID-19 due to the B.1.617.2 (Delta) variant compared to B.1.1.7 (Alpha) variant of SARS-CoV-2: a prospective observational cohort study

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COVID-19 Genomics U. K. (COG-UK) Consortium

Original languageEnglish
Article number10904
Pages (from-to)10904
JournalScientific Reports
Volume12
Issue number1
DOIs
Accepted/In press31 May 2022
Published28 Jun 2022

Bibliographical note

Funding Information: This research was funded in part by the Wellcome Trust (WT213038/Z/18/Z). This work is also supported by the Wellcome Engineering and Physical Sciences Research Council Centre for Medical Engineering at King’s College London (WT203148/Z/16/Z) and the UK Department of Health via the National Institute for Health Research (NIHR) comprehensive Biomedical Research Centre award to Guy’s and St Thomas’ NHS Foundation Trust in partnership with King’s College London and King’s College Hospital NHS Foundation Trust, the Medical Research Council (MRC), and British Heart Foundation. SO and MM are supported by the UK Research and Innovation London Medical Imaging and Artificial Intelligence Centre for Value Based Healthcare. SO is supported by the Wellcome Flagship Programme (WT213038/Z/18/Z). EM is funded by an MRC Skills Development Fellowship Scheme at King’s College London. CHS is supported by the National Core Studies, an initiative funded by United Kingdom Research and Innovation, NIHR, and the Health and Safety Executive, and funded by MRC (MC_PC_20030). CHS is also supported by an Alzheimer’s Society Junior Fellowship (ASJF-170–11). ZOE Limited supported all aspects of building and running the application and service to all users worldwide. For the purpose of open access, the authors have applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission. COG-UK is supported by funding from the Medical Research Council (MRC) part of UK Research & Innovation (UKRI), the National Institute of Health Research (NIHR) [grant code: MC_PC_19027], and Genome Research Limited, operating as the Wellcome Sanger Institute. The authors are grateful to Michael Absoud and Sunil Bhopal for constructive comments on the paper. For the purpose of open access, the authors have applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission. Funding Information: This research was funded in part by the Wellcome Trust (WT213038/Z/18/Z). This work is also supported by the Wellcome Engineering and Physical Sciences Research Council Centre for Medical Engineering at King’s College London (WT203148/Z/16/Z) and the UK Department of Health via the National Institute for Health Research (NIHR) comprehensive Biomedical Research Centre award to Guy’s and St Thomas’ NHS Foundation Trust in partnership with King’s College London and King’s College Hospital NHS Foundation Trust, the Medical Research Council (MRC), and British Heart Foundation. SO and MM are supported by the UK Research and Innovation London Medical Imaging and Artificial Intelligence Centre for Value Based Healthcare. SO is supported by the Wellcome Flagship Programme (WT213038/Z/18/Z). EM is funded by an MRC Skills Development Fellowship Scheme at King’s College London. CHS is supported by the National Core Studies, an initiative funded by United Kingdom Research and Innovation, NIHR, and the Health and Safety Executive, and funded by MRC (MC_PC_20030). CHS is also supported by an Alzheimer’s Society Junior Fellowship (ASJF-170–11). ZOE Limited supported all aspects of building and running the application and service to all users worldwide. For the purpose of open access, the authors have applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission. COG-UK is supported by funding from the Medical Research Council (MRC) part of UK Research & Innovation (UKRI), the National Institute of Health Research (NIHR) [grant code: MC_PC_19027], and Genome Research Limited, operating as the Wellcome Sanger Institute. The authors are grateful to Michael Absoud and Sunil Bhopal for constructive comments on the paper. For the purpose of open access, the authors have applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission. Publisher Copyright: © 2022, The Author(s).

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King's Authors

Abstract

The Delta (B.1.617.2) variant was the predominant UK circulating SARS-CoV-2 strain between May and December 2021. How Delta infection compares with previous variants is unknown. This prospective observational cohort study assessed symptomatic adults participating in the app-based COVID Symptom Study who tested positive for SARS-CoV-2 from May 26 to July 1, 2021 (Delta overwhelmingly the predominant circulating UK variant), compared (1:1, age- and sex-matched) with individuals presenting from December 28, 2020 to May 6, 2021 (Alpha (B.1.1.7) the predominant variant). We assessed illness (symptoms, duration, presentation to hospital) during Alpha- and Delta-predominant timeframes; and transmission, reinfection, and vaccine effectiveness during the Delta-predominant period. 3581 individuals (aged 18 to 100 years) from each timeframe were assessed. The seven most frequent symptoms were common to both variants. Within the first 28 days of illness, some symptoms were more common with Delta versus Alpha infection (including fever, sore throat, and headache) and some vice versa (dyspnoea). Symptom burden in the first week was higher with Delta versus Alpha infection; however, the odds of any given symptom lasting ≥ 7 days was either lower or unchanged. Illness duration ≥ 28 days was lower with Delta versus Alpha infection, though unchanged in unvaccinated individuals. Hospitalisation for COVID-19 was unchanged. The Delta variant appeared more (1.49) transmissible than Alpha. Re-infections were low in all UK regions. Vaccination markedly reduced the risk of Delta infection (by 69-84%). We conclude that COVID-19 from Delta or Alpha infections is similar. The Delta variant is more transmissible than Alpha; however, current vaccines showed good efficacy against disease. This research framework can be useful for future comparisons with new emerging variants.

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