Omicron-associated changes in SARS-CoV-2 symptoms in the United Kingdom

Abstract

Background The SARS-CoV-2 Delta variant has been replaced by the highly transmissible Omicron BA.1 variant, and subsequently by Omicron BA.2. It is important to understand how these changes in dominant variants affect reported symptoms, while also accounting for symptoms arising from other co-circulating respiratory viruses. Methods In a nationally representative UK community study, the COVID-19 Infection Survey, we investigated symptoms in PCR-positive infection episodes vs. PCR-negative study visits over calendar time, by age and vaccination status, comparing periods when the Delta, Omicron BA.1 and BA.2 variants were dominant. Results Between October-2020 and April-2022, 120,995 SARS-CoV-2 PCR-positive episodes occurred in 115,886 participants, with 70,683 (58%) reporting symptoms. The comparator comprised 4,766,366 PCR-negative study visits (483,894 participants); 203,422 (4%) reporting symptoms. Symptom reporting in PCR-positives varied over time, with a marked reduction in loss of taste/smell as Omicron BA.1 dominated, maintained with BA.2 (44%/45% 17 October 2021, 16%/13% 2 January 2022, 15%/12% 27 March 2022). Cough, fever, shortness of breath, myalgia, fatigue/weakness and headache also decreased after Omicron BA.1 dominated, but sore throat increased, the latter to a greater degree than concurrent increases in PCR-negatives. Fatigue/weakness increased again after BA.2 dominated, although to a similar degree to concurrent increases in PCR-negatives. Symptoms were consistently more common in adults aged 18-65 years than in children or older adults. Conclusions Increases in sore throat (also common in the general community), and a marked reduction in loss of taste/smell, make Omicron harder to detect with symptom-based testing algorithms, with implications for institutional and national testing policies.

Differential symptoms among COVID-19 outpatients before and during periods of SARS-CoV-2 Omicron variant dominance in Blantyre, Malawi: a prospective observational study

“…Our data showing a different symptom profile associated with Omicron infection is consistent with studies elsewhere 21 with headache being prominent in three other studies from the UK 21-23 . However, we observed high odds for presenting with fever in presumed Omicron-infected patients than pre-Omicron patients, in contrast with the two studies in the UK 21,23 .…”

“…Our data showing a different symptom profile associated with Omicron infection is consistent with studies elsewhere 21 with headache being prominent in three other studies from the UK 21-23 . However, we observed high odds for presenting with fever in presumed Omicron-infected patients than pre-Omicron patients, in contrast with the two studies in the UK 21,23 . The main differences between the Malawi study and the UK studies are age and prevalence of Omicron sub-lineages, with Malawi cohort being a younger population and having predominantly BA.1 at time of sampling.…”

Comparative symptomatology of infection with SARS-CoV-2 variants Omicron (B.1.1.529) and Delta (B.1.617.2) from routine contact tracing data in England

“…All variables included in the main effects model were selected a priori, consistent with other studies which have considered symptom profiles [7,10,13]. Associations were adjusted for age group, sex, ethnicity, vaccination status, geographical region, and the week in which symptoms began to adjust for potential confounding.…”

“…Another UK survey comparing symptomatic PCR-positive and PCR-negative cases found a marked reduction in reporting of loss of smell and taste, and an increase in sore throat. This survey covered PCR-positives from early to late December 2021, when England moved from a dominant Delta to Omicron [10]. However, over the same period sore throat became more commonly reported in symptomatic PCR-negative cases.…”

The genomic and clinical features of the COVID-19 Omicron variant: a narrative review

“…A recent UK-based study showed that the Omicron variant was strongly associated with symptoms from upper respiratory tract more than the lower respiratory tract. 20 This could be explained by the presence of two Omicron-specific mutations: N764K and N856K. Those mutations were shown to produce cleavage sites for subtilisin-kexin isozyme-1/site-1 protease (SKI-1/S1P) serine protease predominantly situated in the upper airway.…”