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EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-331670

ABSTRACT

Objective To determine how the severity of successively dominant SARS-CoV-2 variants has changed over the course of the COVID-19 pandemic. Design Prospective cohort analysis. Setting Community- and hospital- sequenced COVID-19 cases in the NHS Greater Glasgow and Clyde (NHS GG&C) Health Board (1.2 million people). Participants All sequenced non-nosocomial adult COVID-19 cases in NHS GG&C identified to be infected with the relevant SARS-CoV-2 lineage during the following analysis periods. B.1.177/Alpha analysis: 1st November 2020 - 30th January 2021 (n = 1640). Alpha/Delta analysis: 1st April - 30th June 2021 (n = 5552). AY.4.2 Delta/non-AY.4.2 Delta analysis: 1st July – 31st October 2021 (n = 9613). Non-AY.4.2 Delta/Omicron analysis: 1st – 31st December 2021 (n = 3858). Main outcome measures Admission to hospital, admission to ICU, or death within 28 days of first positive COVID-19 test Results In the B.1.177/Alpha analysis, 300 of 807 (37.2%) B.1.177 cases were recorded as hospitalised or having a more severe outcome, compared to 232 of 833 (27.9%) Alpha cases. After adjusting for the following covariates: age, sex, time of positive test, comorbidities and partial postcode, the cumulative odds ratio was 1.51 (95% central credible interval 1.08-2.11) for Alpha versus B.1.177. In the Alpha/Delta analysis, 113 of 2104 (5.4%) Alpha cases were recorded as hospitalised or having a more severe outcome, compared to 230 of 3448 (6.7%) Delta cases. After adjusting for the above covariates plus number of vaccine doses and reinfection, the cumulative odds ratio was 2.09 (95% central credible interval 1.42-3.08) for Delta versus Alpha. In the non-AY.4.2 Delta/AY.4.2 Delta analysis, 845 of 8644 (9.8%) non-AY.4.2 Delta cases were recorded as hospitalised or having a more severe outcome, compared to 101 of 969 (10.4%) AY.4.2 Delta cases. After adjusting for the previously stated covariates, the cumulative odds ratio was 0.99 (95% central credible interval 0.76-1.27) for AY.4.2 Delta versus non-AY.4.2 Delta. In the non-AY.4.2 Delta/Omicron analysis, 30 of 1164 (2.6%) non-AY.4.2 Delta cases were recorded as hospitalised or having a more severe outcome, compared to 26 of 2694 (1.0%) Omicron cases. After adjusting for the previously listed covariates, the median cumulative odds ratio was 0.49 (95% central credible interval 0.22-1.06) for Omicron versus non-AY.4.2 Delta. Conclusions The direction of change in disease severity between successively emerging SARS-CoV-2 variants of concern was inconsistent. This heterogeneity in virulence between variants, coupled with independent evolutionary emergence, demonstrates that severity associated with future SARS-CoV-2 variants is inherently unpredictable.

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