Epidemiological analysis of the first 1000 cases of SARS-CoV-2 lineage BA.1 (B.1.1.529, Omicron) compared with co-circulating Delta in Wales, UK

Pacchiarini, Nicole, Sawyer, Clare, Williams, Christopher, Sutton, Daryn, Roberts, Christopher, Simkin, Felicity, King, Grace, McClure, Victoria, Cottrell, Simon, Clayton, Helen, Beazer, Andrew, Williams, Catie, Rey, Sara M., Connor, Thomas R. ORCID: https://orcid.org/0000-0003-2394-6504 and Moore, Catherine 2022. Epidemiological analysis of the first 1000 cases of SARS-CoV-2 lineage BA.1 (B.1.1.529, Omicron) compared with co-circulating Delta in Wales, UK. Influenza and Other Respiratory Viruses 16 (6) , pp. 986-993. 10.1111/irv.13021

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Abstract

Background The Omicron (lineage B.1.1.529) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first reported in Wales, UK, on 3 December 2021. The aim of the study was to describe the first 1000 cases of the Omicron variant by demographic, vaccination status, travel and severe outcome status and compare this to contemporaneous cases of the Delta variant. Methods Testing, typing and contact tracing data were collected by Public Health Wales and analysis undertaken by the Communicable Disease Surveillance Centre (CDSC). Risk ratios for demographic factors and symptoms were calculated comparing Omicron cases to Delta cases identified over the same time period. Results By 14 December 2021, 1000 cases of the Omicron variant had been identified in Wales. Of the first 1000, just 3% of cases had a prior history of travel revealing rapid community transmission. A higher proportion of Omicron cases were identified in individuals aged 20–39, and most cases were double vaccinated (65.9%) or boosted (15.7%). Age-adjusted analysis also revealed that Omicron cases were less likely to be hospitalised (0.4%) or report symptoms (60.8%). Specifically a significant reduction was observed in the proportion of Omicron cases reporting anosmia (8.9%). Conclusion Key findings include a lower risk of anosmia and a reduced risk of hospitalisation in the first 1000 Omicron cases compared with co-circulating Delta cases. We also identify that existing measures for travel restrictions to control importations of new variants identified outside the United Kingdom did not prevent the rapid ingress of Omicron within Wales.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Biosciences
Additional Information:	This is an open access article under the terms of the Creative Commons Attribution License
Publisher:	Wiley Open Access
ISSN:	1750-2640
Date of First Compliant Deposit:	25 July 2022
Date of Acceptance:	12 June 2022
Last Modified:	18 May 2023 09:54
URI:	https://orca.cardiff.ac.uk/id/eprint/151434

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