The Household Secondary Attack Rate of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): A Rapid Review

Abstract

Background Although much of the public health effort to combat COVID-19 has focused on disease control strategies in public settings, transmission of SARS-CoV-2 within households remains an important problem. The nature and determinants of household transmission are poorly understood. Methods To address this gap, we gathered and analyzed data from 22 published and pre-published studies from 10 countries (20,291 household contacts) that were available through September 2, 2020. Our goal was to combine estimates of the SARS-CoV-2 household secondary attack rate (SAR) and explore variation in estimates of the household SAR. Results The overall pooled random-effects estimate of the household SAR was 17.1% (95% CI: 13.7-21.2%). In study-level, random-effects meta-regressions stratified by testing frequency (1 test, 2 tests, >2 tests), SAR estimates were 9.2% (95% CI: 6.7-12.3%), 17.5% (95% CI: 13.9-21.8%), and 21.3% (95% CI: 13.8-31.3%), respectively. Household SAR tended to be higher among older adult contacts and among contacts of symptomatic cases. Conclusions These findings suggest that SAR reported using a single follow-up test may be underestimated and that testing household contacts of COVID-19 cases on multiple occasions may increase the yield for identifying secondary cases.

High infection attack rates of SARS-CoV-2 in Dutch households revealed by dense sampling

“…High estimated SARs are also in line with observations from surveillance data and cluster reports that the household is the most frequently reported setting of infection [26]. Our study differs from earlier household studies for SAR-CoV-2 in that we observed substantially higher SARs [11, 27]. In fact, only a few studies reported estimates that were somewhat similar to our estimates (32%-38% vs 43%) [28, 29].…”

Risk factors and action thresholds for the novel coronavirus pandemic. Insights from the Italian Society of Nephrology COVID-19 Survey

“…As stated in the survey questionnaire [ 1 ], we collected only information concerning the number of total and positive TX patients at the center level and not their individual data, such as transplant history, blood chemistry and immunosuppressive therapy. Nonetheless, it can be argued that any person, be they immunocompetent or immunosuppressed, who comes into contact with a formerly unknown virus has the same susceptibility to the infection, but the consequences are likely to be more severe in immunosuppressed organ transplant recipients [ 26 ]. The preliminary evidence reviewed by Thng [ 27 ] supports this hypothesis, although further prospective studies are needed to provide conclusive data.…”

Household Transmission of SARS-CoV-2

“…To assess the methodological quality and risk of bias of included studies of SARS-CoV-2, we used the same modified version of the Newcastle-Ottawa quality assessment scale for observational studies used by Fung et al . 10 , 11 Studies received as many as 9 points based on participant selection (4 points), study comparability (1 point), and outcome of interest (4 points). Studies were classified as having high (≤3 points), moderate (4-6 points), and low (≥7 points) risk of bias.…”