SynthesisPloS one2020
What do we know about SARS-CoV-2 transmission? A systematic review and meta-analysis of the secondary attack rate and associated risk factors.
Synthesis in PloS one, 2020. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 126 papers, 12 of them syntheses that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
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.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
126 citing papers in PubMed, 12 syntheses or guidelines pooled it.
- Systematic Review and Meta-Analysis of Emerging Viral Zoonotic Diseases, 2016-2026.Transboundary and emerging diseases · 2026Pooled it
- Impact of disease severity, age, sex, comorbidity, and vaccination on secondary attack rates of SARS-CoV-2: a global systematic review and meta-analysis.BMC infectious diseases · 2025Pooled it
- Superspreading of SARS-CoV-2: a systematic review and meta-analysis of event attack rates and individual transmission patterns.Epidemiology and infection · 2024Pooled it
- Pooled it
- Pooled it
- The role of children in household transmission of COVID-19: a systematic review and meta-analysis.International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases · 2022Pooled it
- Transmission of SARS-CoV-2 in standardised first few X cases and household transmission investigations: A systematic review and meta-analysis.Influenza and other respiratory viruses · 2022Pooled it
- Transmissibility and pathogenicity of the severe acute respiratory syndrome coronavirus 2: A systematic review and meta-analysis of secondary attack rate and asymptomatic infection.Journal of infection and public health · 2022Pooled it
- Measures implemented in the school setting to contain the COVID-19 pandemicThe Cochrane database of systematic reviews · 2022Pooled it
- Epidemiological, Radiographical, and Laboratorial Characteristics of Chinese Asymptomatic Cases With COVID-19: A Systematic Review and Meta-Analysis.Frontiers in public health · 2022Pooled it
- Non-pharmacological measures implemented in the setting of long-term care facilities to prevent SARS-CoV-2 infections and their consequences: a rapid review.The Cochrane database of systematic reviews · 2021Pooled it
- Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Setting-specific Transmission Rates: A Systematic Review and Meta-analysis.Clinical infectious diseases : an official publication of the Infectious Diseases Society of America · 2021Pooled it
- Trial
- Evaluating adherence to COVID-19 quarantine protocols at two international ground crossings in Savannakhet Province, Lao PDR.Tropical medicine and health · 2026Article
- Navigating Equitable Access to Cancer and Mental Health Services During Pandemics: Stakeholder Perspectives on COVID-19 Challenges and Community-Based Solutions for Immigrants and Refugees-Proceedings from Think Tank Sessions.Healthcare (Basel, Switzerland) · 2025Article
- Impact of tiered restrictions in December 2020 on COVID-19 hospitalisations in England: a synthetic control study.BMJ open · 2025Observational
- Detecting and quantifying heterogeneity in susceptibility using contact tracing data.PLoS computational biology · 2024Article
- Risk mapping of respiratory viral transmission and disease severity using individual and environmental health parameters: A scoping review and protocol analysis.One health (Amsterdam, Netherlands) · 2024Review
- Household secondary attack rate amongst the susceptible contacts of COVID-19 cases and its epidemiological profile: A retrospective study from central Gujarat, India.Journal of family medicine and primary care · 2024Article
- SARS-CoV-2 Seroprevalence in a Berlin Kindergarten Environment: A Cross-Sectional Study, September 2021.Children (Basel, Switzerland) · 2024Article
66 more citing papers are in PubMed but not listed here.
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
12 authors.
Funding
Abstract
introductionCurrent SARS-CoV-2 containment measures rely on controlling viral transmission. Effective prioritization can be determined by understanding SARS-CoV-2 transmission dynamics. We conducted a systematic review and meta-analyses of the secondary attack rate (SAR) in household and healthcare settings. We also examined whether household transmission differed by symptom status of index case, adult and children, and relationship to index case.
methodsWe searched PubMed, medRxiv, and bioRxiv databases between January 1 and July 25, 2020. High-quality studies presenting original data for calculating point estimates and 95% confidence intervals (CI) were included. Random effects models were constructed to pool SAR in household and healthcare settings. Publication bias was assessed by funnel plots and Egger's meta-regression test.
results43 studies met the inclusion criteria for household SAR, 18 for healthcare SAR, and 17 for other settings. The pooled household SAR was 18.1% (95% CI: 15.7%, 20.6%), with significant heterogeneity across studies ranging from 3.9% to 54.9%. SAR of symptomatic index cases was higher than asymptomatic cases (RR: 3.23; 95% CI: 1.46, 7.14). Adults showed higher susceptibility to infection than children (RR: 1.71; 95% CI: 1.35, 2.17). Spouses of index cases were more likely to be infected compared to other household contacts (RR: 2.39; 95% CI: 1.79, 3.19). In healthcare settings, SAR was estimated at 0.7% (95% CI: 0.4%, 1.0%). DISCUSSION: While aggressive contact tracing strategies may be appropriate early in an outbreak, as it progresses, measures should transition to account for setting-specific transmission risk. Quarantine may need to cover entire communities while tracing shifts to identifying transmission hotspots and vulnerable populations. Where possible, confirmed cases should be isolated away from the household.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.