PLoS ONE (Jan 2024)

COVID-19 in non-hospitalised adults caused by either SARS-CoV-2 sub-variants Omicron BA.1, BA.2, BA.4/5 or Delta associates with similar illness duration, symptom severity and viral kinetics, irrespective of vaccination history.

  • Hermaleigh Townsley,
  • Joshua Gahir,
  • Timothy W Russell,
  • David Greenwood,
  • Edward J Carr,
  • Matala Dyke,
  • Lorin Adams,
  • Murad Miah,
  • Bobbi Clayton,
  • Callie Smith,
  • Mauro Miranda,
  • Harriet V Mears,
  • Chris Bailey,
  • James R M Black,
  • Ashley S Fowler,
  • Margaret Crawford,
  • Katalin Wilkinson,
  • Matthew Hutchinson,
  • Ruth Harvey,
  • Nicola O'Reilly,
  • Gavin Kelly,
  • Robert Goldstone,
  • Rupert Beale,
  • Padmasayee Papineni,
  • Tumena Corrah,
  • Richard Gilson,
  • Simon Caidan,
  • Jerome Nicod,
  • Steve Gamblin,
  • George Kassiotis,
  • Vincenzo Libri,
  • Bryan Williams,
  • Sonia Gandhi,
  • Adam J Kucharski,
  • Charles Swanton,
  • David L V Bauer,
  • Emma C Wall

DOI
https://doi.org/10.1371/journal.pone.0294897
Journal volume & issue
Vol. 19, no. 3
p. e0294897

Abstract

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BackgroundSARS-CoV-2 variant Omicron rapidly evolved over 2022, causing three waves of infection due to sub-variants BA.1, BA.2 and BA.4/5. We sought to characterise symptoms and viral loads over the course of COVID-19 infection with these sub-variants in otherwise-healthy, vaccinated, non-hospitalised adults, and compared data to infections with the preceding Delta variant of concern (VOC).MethodsIn a prospective, observational cohort study, healthy vaccinated UK adults who reported a positive polymerase chain reaction (PCR) or lateral flow test, self-swabbed on alternate weekdays until day 10. We compared participant-reported symptoms and viral load trajectories between infections caused by VOCs Delta and Omicron (sub-variants BA.1, BA.2 or BA.4/5), and tested for relationships between vaccine dose, symptoms and PCR cycle threshold (Ct) as a proxy for viral load using Chi-squared (χ2) and Wilcoxon tests.Results563 infection episodes were reported among 491 participants. Across infection episodes, there was little variation in symptom burden (4 [IQR 3-5] symptoms) and duration (8 [IQR 6-11] days). Whilst symptom profiles differed among infections caused by Delta compared to Omicron sub-variants, symptom profiles were similar between Omicron sub-variants. Anosmia was reported more frequently in Delta infections after 2 doses compared with Omicron sub-variant infections after 3 doses, for example: 42% (25/60) of participants with Delta infection compared to 9% (6/67) with Omicron BA.4/5 (χ2 P ConclusionOur study emphasises both the changing symptom profile of COVID-19 infections in the Omicron era, and ongoing transmission risk of Omicron sub-variants in vaccinated adults.Trial registrationNCT04750356.