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

, COVID-19 Genomics UK (COG-UK) Consortium (2021) Exponential growth, high prevalence of SARS-CoV-2, and vaccine effectiveness associated with the Delta variant. Science, 374 (6574). ISSN 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:
Journal Article
Journal or Publication Title:
Science
ID Code:
166211
Deposited By:
Deposited On:
16 Feb 2022 12:55
Refereed?:
Yes
Published?:
Published
Last Modified:
04 May 2022 02:43