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A Comparison of Symptom Prevalence, Severity and Duration in the SARS-CoV-2 Omicron Versus Delta Variants Among Vaccinated Individuals from the ZOE COVID Study
20 Pages Posted: 8 Feb 2022
More...Abstract
Background: The most recent dominant SARS-CoV-2 variant of concern, Omicron, maybe less severe than the previously dominant variant, Delta. The aim of this study is to quantify the differences in their symptoms, severity, and duration among the vaccinated (two or three doses) population in the UK.
Methods: 62,002 UK participants from the ZOE COVID App testing positive for SARS-CoV-2 and reporting symptoms were matched 1:1 on age, sex, and vaccination dose across two periods: from June 1st, 2021, to November 27th, 2021, (Delta dominant, N=4,990) and from December 22nd, 2021, to January 17th, 2022 (Omicron dominant, N=4,990). We compared the prevalence of the 32 COVID-19 related symptoms, their duration, and the severity of the acute infection.
Results: The symptoms of infection with Omicron were significantly different from those by the Delta variant. For Omicron, loss of smell was less prevalent (16.7% versus 52.7%, OR = 0.17 [95%CI: 0.16 - 0.19], p<0.001) and sore throat was more frequent (70.5% versus 60.8%, OR = 1.55 [95%CI: 1.43 -1.69], p<0.001). The duration of symptoms was significantly shorter (6.87 [95%CI: 6.58 - 7.16] days, versus 8.89 [95%CI: 8.61 - 9.17] days) and there was a lower rate of hospitalisation (1.9% versus 2.6%, OR = 0.75 [0.57 - 0.98], p = 0.03).
Interpretation: The prevalence of symptoms that characterise an Omicron infection differ from those of the Delta SARS-CoV-2 variant, with apparently less involvement of the lower respiratory tract, need for hospitalisation, and a shorter duration of the acute phase in vaccinated people.
Funding Information: ZOE, NIHR, CDRF, NIH, MRC.
Declaration of Interests: TDS, AMV, CJS and SO are consultants to Zoe Ltd (“Zoe”). JW, AM, LP, SP and JC are employees of Zoe Ltd. Other authors have no conflict of interest to declare.
Ethics Approval Statement: Ethical approval for use of the app for research purposes in the UK was obtained from King’s College London Ethics Committee (review reference LRS 19/20-18210), and all users provided consent for non-commercial use.
Keywords: covid-19, variants of concern, Omicron, Delta, vaccination, SARS-CoV-2
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