Exponential growth, high prevalence of SARS-CoV-2, and vaccine effectiveness associated with the Delta variant.
Science
; 374(6574): eabl9551, 2021 Dec 17.
Article
in English
| MEDLINE | ID: covidwho-1494927
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 Transmission1 (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.
Full text:
Available
Collection:
International databases
Database:
MEDLINE
Main subject:
COVID-19 Vaccines
/
SARS-CoV-2
/
COVID-19
/
Vaccine Efficacy
Type of study:
Diagnostic study
/
Experimental Studies
/
Observational study
/
Randomized controlled trials
Topics:
Vaccines
/
Variants
Limits:
Adolescent
/
Adult
/
Aged
/
Child
/
Child, preschool
/
Female
/
Humans
/
Male
/
Middle aged
/
Young adult
Country/Region as subject:
Europa
Language:
English
Journal:
Science
Year:
2021
Document Type:
Article
Affiliation country:
Science.abl9551
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