Observational studyLancet (London, England)2022
Symptom prevalence, duration, and risk of hospital admission in individuals infected with SARS-CoV-2 during periods of omicron and delta variant dominance: a prospective observational study from the ZOE COVID Study.
Observational study in Lancet (London, England), 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. It is linked to trial NCT05947643 (Smell in COVID-19 and Efficacy of Nasal Theophylline 3), which is not on this map. Cited by 506 papers, 4 of them syntheses that pooled it.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Smell in COVID-19 and Efficacy of Nasal Theophylline 3
Who cites it
506 citing papers in PubMed, 4 syntheses or guidelines pooled it.
- Oral Manifestations in the Post COVID-19 Condition: A Systematic Review With Meta-Analysis.Reviews in medical virology · 2025Pooled it
- Trends in symptom prevalence and sequential onset of SARS-CoV-2 infection from 2020 to 2022 in East and Southeast Asia: a trajectory pattern exploration based on summary data.Archives of public health = Archives belges de sante publique · 2024Pooled it
- New variants of COVID-19 (XBB.1.5 and XBB.1.16, the "Arcturus"): A review of highly questioned concerns, a brief comparison between different peaks in the COVID-19 pandemic, with a focused systematic review on expert recommendations for prevention, vaccination, and treatment measures in the general population and at-risk groups.Immunity, inflammation and disease · 2024Pooled it
- Comparison of Omicron and Delta Variants of SARS-CoV-2: A Systematic Review of Current Evidence.Infectious disorders drug targets · 2024Pooled it
- A randomized, double-blind, placebo-controlled trial of niclosamide nanohybrid for the treatment of patients with mild to moderate COVID-19.Nature communications · 2025Trial
- Jieji Xuanfei Chuyi granules in the treatment of COVID-19: A randomized, open-label, parallel-controlled clinical trial.Medicine · 2025Trial
- Randomised, Placebo-Controlled, Double-Blind Trial to Assess Efficacy and Safety of ELOM-080 in Outpatients with COVID-19.Advances in therapy · 2025Trial
- COVID-19 Rebound After VV116 vs Nirmatrelvir-Ritonavir Treatment: A Randomized Clinical Trial.JAMA network open · 2024Trial
- Estimating the potential public health and economic impact of vaccination timing: A modeling study of COVID-19 vaccination in the United Kingdom.Human vaccines & immunotherapeutics · 2026Article
- Calculating the Probability that a Previously Susceptible Individual is Infected as a Function of Time Following Exposure to SARS-CoV-2.Infectious diseases and therapy · 2026Article
- A TriNetX global collaborative network retrospective cohort study on the impact of COVID-19 vaccination on juvenile idiopathic arthritis.Scientific reports · 2026Article
- Monitoring viral evolution and epidemiological characteristics of SARS-CoV-2 during 2022-2023 using Integrated Genomic Surveillance.Communications medicine · 2026Article
- Variant-Independent Association Between Clinical Symptoms and IgM/IgG Responses During the Transition from Pre-Omicron to Omicron SARS-CoV-2 Infections.Microorganisms · 2026Article
- A High-Throughput Platform for Rapid Adaptation of DNA Aptamers to SARS-CoV-2 Evolution.bioRxiv : the preprint server for biology · 2026Article
- Co-prevalence of SARS-CoV-2 and Noroviruses in Wastewater Collection and Treatment Facilities of the Eastern Cape Region, South Africa: An Exacerbated Public and Environmental Health Risk Concern.Food and environmental virology · 2026Article
- Infants' General Movements Were Not Affected by Exposure to Maternal Severe Acute Respiratory Syndrome Coronavirus 2 Infections.Acta paediatrica (Oslo, Norway : 1992) · 2026Observational
- Considerations for epidemiological studies investigating emerging post-acute infection syndromes: Long Covid as a case study.EClinicalMedicine · 2026Review
- Article
- Longitudinal Epidemiology and Variant Dynamics of SARS-CoV-2 in Coastal Kenya (2020-2025): Clinical Features and Wave Patterns.Open forum infectious diseases · 2026Article
- Article
446 more citing papers are in PubMed but not listed here.
Corrections and comments
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Authors and funding
24 authors.
Funding
Abstract
backgroundThe SARS-CoV-2 variant of concern, omicron, appears to be less severe than delta. We aim to quantify the differences in symptom prevalence, risk of hospital admission, and symptom duration among the vaccinated population.
methodsIn this prospective longitudinal observational study, we collected data from participants who were self-reporting test results and symptoms in the ZOE COVID app (previously known as the COVID Symptoms Study App). Eligible participants were aged 16-99 years, based in the UK, with a body-mass index between 15 and 55 kg/m
findingsBetween June 1, 2021, and Jan 17, 2022, we identified 63 002 participants who tested positive for SARS-CoV-2 and reported symptoms in the ZOE app. These patients were matched 1:1 for age, sex, and vaccination dose, across two periods (June 1 to Nov 27, 2021, delta prevalent at >70%; n=4990, and Dec 20, 2021, to Jan 17, 2022, omicron prevalent at >70%; n=4990). Loss of smell was less common in participants infected during omicron prevalence than during delta prevalence (16·7% vs 52·7%, odds ratio [OR] 0·17; 95% CI 0·16-0·19, p<0·001). Sore throat was more common during omicron prevalence than during delta prevalence (70·5% vs 60·8%, 1·55; 1·43-1·69, p<0·001). There was a lower rate of hospital admission during omicron prevalence than during delta prevalence (1·9% vs 2·6%, OR 0·75; 95% CI 0·57-0·98, p=0·03).
interpretationThe prevalence of symptoms that characterise an omicron infection differs from those of the delta SARS-CoV-2 variant, apparently with less involvement of the lower respiratory tract and reduced probability of hospital admission. Our data indicate a shorter period of illness and potentially of infectiousness which should impact work-health policies and public health advice.
fundingWellcome Trust, ZOE, National Institute for Health Research, Chronic Disease Research Foundation, National Institutes of Health, and Medical Research Council.
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