Association of SARS-CoV-2 viral load distributions with individual demographics and suspected variant type: Results from the Liverpool Community Testing Pilot - England, 6 November 2020‒8 September 2021

Hughes, David ORCID: 0000-0002-1287-9994, Cheyne, Chris, Ashton, Matthew, Coffee, Emer, Crozier, Alex, Semple, Malcolm ORCID: 0000-0001-9700-0418, Buchan, Iain ORCID: 0000-0003-3392-1650 and Garcia-Finana, Marta ORCID: 0000-0003-4939-0575 (2023) Association of SARS-CoV-2 viral load distributions with individual demographics and suspected variant type: Results from the Liverpool Community Testing Pilot - England, 6 November 2020‒8 September 2021. Eurosurveillance, 28 (4). pp. 18-31.

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Abstract

Background: PCR cycle threshold (CT) is a proxy measure of the viral load of an individual testing positive for SARS-CoV-2. CT value may change by age and suspected variant type. Methods: We considered all positive PCR results from Cheshire and Merseyside between 6th November 2020 and 8th September 2021. Kernel density estimates were used to inspect CT distributions. Multivariable quantile regression models assessed associations between demographic features and CT. Results: We report PCR CT values for 188,821 individuals who tested positive for COVID-19. Multivariable quantile regression modelling shows reduced median CT values as age increases for suspected wild-type and Alpha, but not for Delta. 5-11-year-olds, for example, exhibited higher CT values than 30-39-year-olds (median age) with 1.8 (95%CI 1.5-2.1), 2.2 (1.8-2.6) and 0.8 (0.6-0.9) thresholds higher for suspected wild-type, Alpha and Delta positives respectively. 12-18-year-olds reported higher CT values for wild-type and Alpha positives, but not for Delta. Suspected Delta positives reported 2.8 cycle thresholds lower than wild-type COVID-19 (95% CI (2.7-2.8), p<0.001). Suspected Alpha positives, were associated with lower CT than wild type COVID-19 by 1.5 cycle thresholds (95% CI (1.4-1.5), p<0.001). Conclusions: Individuals with suspected Alpha or Delta variants had higher viral loads, suggesting increased transmission risk. School aged children with suspected wild-type or alpha variants may play a smaller role in transmission than adults, although have greater mixing exposures. Smaller changes in viral loads were observed with age with the suspected Delta variant. Age and dominant variant should be considered when developing COVID transmission control strategies. Keywords: PCR cycle thresholds; COVID-19; age; variant; viral load

Item Type:	Article
Uncontrolled Keywords:	Humans, Viral Load, Demography, Adolescent, Adult, Child, England, Pandemics, COVID-19, SARS-CoV-2
Divisions:	Faculty of Health and Life Sciences Faculty of Health and Life Sciences > Institute of Population Health
Depositing User:	Symplectic Admin
Date Deposited:	21 Nov 2022 09:21
Last Modified:	11 Oct 2023 14:45
DOI:	10.2807/1560-7917.ES.2023.28.4.2200129
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3166277