COVID-19 in non-hospitalised adults caused by either SARS-CoV-2 sub-variants Omicron BA.1, BA.2, BA.5 or Delta associates with similar illness duration, symptom severity and viral kinetics, irrespective of vaccination history

Abstract

Introduction The impact of COVID-19 vaccination on disease in the community has been limited, as a result of both SARS-CoV-2 Variants of Concern that partially escape vaccine-induced immunity. We sought to characterise symptoms and viral loads over the course of COVID-19 infection in otherwise-healthy vaccinated adults, representative of the general population, to assess whether current self-isolation guidance remains justified. Methods In a prospective, observational cohort study, healthy vaccinated UK adults who reported a positive PCR or lateral flow test, self-swabbed on alternate days until day 10. We compared symptoms and viral kinetics between infections caused by VOCs Delta and Omicron (sub-variants BA.1 and BA.2) and investigated applicability of UK NHS isolation guidelines to these newer VOCs. Results 373 infection episodes were reported among 349 participants. Across VOCs, symptom duration was similar, however symptom profiles differed significantly among infections caused by Delta, Omicron BA.1 and BA.2. Anosmia was reported in <10% of participants with BA.1 and BA.2, compared to 42% with Delta infection, coryza fatigue and myalgia predominated. Most notably, viral load trajectories and peaks did not differ between Delta, BA.1 and BA.2, irrespective of symptom severity, VOC or vaccination status. Conclusion COVID-19 isolation guidance should not differ based on symptom severity or febrile illness and must remain under review as new SARS-CoV-2 VOCs emerge and population immunity changes. Our study emphasises the ongoing transmission risk of Omicron sub-variants in vaccinated adults with mild symptoms that may extend beyond current isolation periods.

The association between SARS-CoV-2 infections in English primary and secondary school children and staff, and infections in members of their household in the schoolyear 2020-2021: a self-controlled case-series analysis

“…17 Previous studies have shown SARS-CoV-2 to be infectious up to 7-10 days following reporting of symptoms, and that infectiousness rarely continues more than 10 days. 26,27 This is reflected in our findings with IRRs attenuated towards the null in the 8-14 days following household infection, but the evidence for an increased IRR in this period compared with baseline is still pronounced, and may be consistent with some delay from testing and reporting. 28,29…”

Infectious viral shedding of SARS-CoV-2 Delta following vaccination: A longitudinal cohort study

“…Measurement bias from self-reported symptoms may have occurred from recall error and viral variant differences among participants. Differences in viral load may have had an effect on the day of symptom onset in participants relative to initial infection, as variant-specific changes in symptom outcomes have been reported [44]. Furthermore, unvaccinated individuals in our analysis were mostly enrolled prior to the emergence and global spread of the Delta lineage, whereas fully vaccinated individuals were almost exclusively enrolled once Delta was the dominant circulating lineage.…”

Accurate evaluation of live-virus microneutralization for SARS-CoV-2 variant JN.1

“…The UCLH-Crick Legacy study (NCT04750356) is a prospective observational cohort, established in January 2021 to investigate longitudinal immunity to SARS-CoV-2. Extensive descriptions of the cohort can be found in our prior reports 7-10,14,15,25 . In the UK, from September 2023, healthcare workers, adults over 65 years, and those with either immunocompromised or caring responsibilities were offered a dose of COVID-19 vaccine as a 5 th dose booster.…”

“…The UCLH-Crick Legacy study (NCT04750356) is a prospective observational cohort, established in January 2021 to investigate longitudinal immunity to SARS-CoV-2. Extensive descriptions of the cohort can be found in our prior reports [7][8][9][10]14,15,25 Legacy participants were included in this study if they received their fifth dose of COVID-19 vaccine (BNT162b2+BA4/5 or BNT162b2-XBB.1.5) after August 1st 2023 and had a preboost sample taken more than 2 weeks after a previous dose and/or a post-boost sample within 4 weeks of a fifth dose 7 . We also analysed a subset of participants who contributed paired pre-and post-vaccination serum samples 7 .…”

“…below. Omicron sub-variants isolated at the Francis Crick Institute were collected from Legacy participants reporting acute symptomatic infection, following previously described active surveillance protocols25 .…”