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.
Creators: name: Townsley, Hermaleigh
name: Gahir, Joshua
name: Russell, Timothy W
name: Greenwood, David
name: Carr, Edward J
name: Dyke, Matala
name: Adams, Lorin
name: Miah, Murad
name: Clayton, Bobbi
name: Smith, Callie
name: Miranda, Mauro
name: Mears, Harriet V
name: Bailey, Chris
name: Black, James RM
name: Fowler, Ashley S
name: Crawford, Margaret
name: Wilkinson, Katalin
name: Hutchinson, Matthew
name: Harvey, Ruth
name: O'Reilly, Nicola
name: Kelly, Gavin
name: Goldstone, Robert
name: Beale, Rupert
name: Papineni, Padmasayee
name: Corrah, Tumena
name: Gilson, Richard
name: Caidan, Simon
name: Nicod, Jerome
name: Gamblin, Steve
name: Kassiotis, George
name: Libri, Vincenzo
name: Williams, Bryan
name: Gandhi, Sonia
name: Kucharski, Adam J
name: Swanton, Charles
name: Bauer, David LV
name: Wall, Emma C
Publisher: name: The Francis Crick Institute
Year: 2024
Subjects: classificationCode: Tumour Biology
subject: Tumour Biology
classificationCode: Stem Cells
subject: Stem Cells
classificationCode: Signalling & Oncogenes
subject: Signalling &amp; Oncogenes
classificationCode: Chemical Biology & High Throughput
subject: Chemical Biology &amp; High Throughput
classificationCode: Ecology,Evolution & Ethology
subject: Ecology,Evolution &amp; Ethology
classificationCode: Infectious Disease
subject: Infectious Disease
classificationCode: Immunology
subject: Immunology
subject: FOS: Clinical medicine
classificationCode: Genetics & Genomics
subject: Genetics &amp; Genomics
classificationCode: Computational & Systems Biology
subject: Computational &amp; Systems Biology
classificationCode: Genome Integrity & Repair
subject: Genome Integrity &amp; Repair
classificationCode: Neurosciences
subject: Neurosciences
classificationCode: Human Biology & Physiology
subject: Human Biology &amp; Physiology
classificationCode: Model organisms
subject: Model organisms
classificationCode: Cell Biology
subject: Cell Biology

description: BACKGROUND: SARS-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). METHODS: In 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. RESULTS: 563 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 &lt; 0.001; OR 7.3 [95% CI 2.7-19.4]). Fever was less common with Delta (20/60 participants; 33%) than Omicron BA.4/5 (39/67; 58%; χ2 P = 0.008; OR 0.4 [CI 0.2-0.7]). Amongst infections with an Omicron sub-variants, symptoms of coryza, fatigue, cough and myalgia predominated. Viral load trajectories and peaks did not differ between Delta, and Omicron, irrespective of symptom severity (including asymptomatic participants), VOC or vaccination status. PCR Ct values were negatively associated with time since vaccination in participants infected with BA.1 (β = -0.05 (CI -0.10-0.01); P = 0.031); however, this trend was not observed in BA.2 or BA.4/5 infections. CONCLUSION: Our 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 REGISTRATION: NCT04750356.