Viral burden is associated with age, vaccination, and viral variant in a population-representative study of SARS-CoV-2 that accounts for time-since-infection-related sampling bias

The COVID-19 Genomics UK (COG-UK) Consortium, Helen R. Fryer*, Tanya Golubchik, Matthew Hall, Christophe Fraser, Robert Hinch, Luca Ferretti, Laura Thomson, Anel Nurtay, Lorenzo Pellis, Thomas House, George MacIntyre-Cockett, Amy Trebes, David Buck, Paolo Piazza, Angie Green, Lorne J. Lonie, Darren Smith, Matthew Bashton, Matthew CrownAndrew Nelson, Clare M McCann, Mohammed (Adnan) Tariq, Claire Elstob, Rui Nunes Dos Santos, Zack Richards, Xin Xhang, Joseph Hawley, Mark R Lee, Priscilla Carrillo-Barragan, Isobel Chapman, Sarah Harthern-Flint, David Bonsall, Katrina A. Lythgoe

*Corresponding author for this work

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Abstract

In this study, we evaluated the impact of viral variant, in addition to other variables, on within-host viral burden, by analysing cycle threshold (Ct) values derived from nose and throat swabs, collected as part of the UK COVID-19 Infection Survey. Because viral burden distributions determined from community survey data can be biased due to the impact of variant epidemiology on the time-since-infection of samples, we developed a method to explicitly adjust observed Ct value distributions to account for the expected bias. By analysing the adjusted Ct values using partial least squares regression, we found that among unvaccinated individuals with no known prior exposure, viral burden was 44% lower among Alpha variant infections, compared to those with the predecessor strain, B.1.177. Vaccination reduced viral burden by 67%, and among vaccinated individuals, viral burden was 286% higher among Delta variant, compared to Alpha variant, infections. In addition, viral burden increased by 17% for every 10-year age increment of the infected individual. In summary, within-host viral burden increases with age, is reduced by vaccination, and is influenced by the interplay of vaccination status and viral variant.

Original languageEnglish
Article numbere1011461
JournalPLoS Pathogens
Volume19
Issue number8
DOIs
Publication statusPublished - 14 Aug 2023

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