Exponential growth, high prevalence of SARS-CoV-2, and vaccine effectiveness associated with the Delta variant


Elliott, Paul, Haw, David ORCID: 0000-0002-9228-0542, Wang, Haowei, Eales, Oliver, Walters, Caroline E, Ainslie, Kylie EC, Atchison, Christina, Fronterre, Claudio, Diggle, Peter J, Page, Andrew J et al (show 10 more authors) (2021) Exponential growth, high prevalence of SARS-CoV-2, and vaccine effectiveness associated with the Delta variant SCIENCE, 374 (6574). 1463-+. ISSN 0036-8075, 1095-9203

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Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections were rising during early summer 2021 in many countries as a result of the Delta variant. We assessed reverse transcription polymerase chain reaction swab positivity in the Real-time Assessment of Community Transmission–1 (REACT-1) study in England. During June and July 2021, we observed sustained exponential growth with an average doubling time of 25 days, driven by complete replacement of the Alpha variant by Delta and by high prevalence at younger, less-vaccinated ages. Prevalence among unvaccinated people [1.21% (95% credible interval 1.03%, 1.41%)] was three times that among double-vaccinated people [0.40% (95% credible interval 0.34%, 0.48%)]. However, after adjusting for age and other variables, vaccine effectiveness for double-vaccinated people was estimated at between ~50% and ~60% during this period in England. Increased social mixing in the presence of Delta had the potential to generate sustained growth in infections, even at high levels of vaccination.

Item Type: Article
Uncontrolled Keywords: COVID-19 Genomics UK (COG-UK) Consortium11‡, Humans, Hospitalization, Prevalence, Family Characteristics, Age Factors, Socioeconomic Factors, Adolescent, Adult, Aged, Middle Aged, Child, Child, Preschool, England, Female, Male, Young Adult, Self Report, Vaccination Coverage, COVID-19, SARS-CoV-2, COVID-19 Vaccines, COVID-19 Nucleic Acid Testing, Ethnicity, Vaccine Efficacy
Divisions: Faculty of Health & Life Sciences
Faculty of Health & Life Sciences > Inst. Infection, Vet & Ecological Sciences
Depositing User: Symplectic Admin
Date Deposited: 09 May 2022 08:49
Last Modified: 16 Jun 2026 13:34
DOI: 10.1126/science.abl9551
Open Access URL: https://doi.org/10.1126/science.abl9551
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3154483
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