Household Secondary Attack Rate of COVID-19 and Associated Determinants in Guangzhou, China: A Retrospective Cohort Study
Abstract
Summary Background As of May 8, 2020, the global reported number of COVID-19 cases has crossed over 3.8 million with nearly 270,000 deaths. The household transmissibility of SARS-CoV-2, the causative pathogen, remains elusive. Methods Based on a comprehensive contact-tracing dataset from Guangzhou, we estimated the secondary attack rate (SAR) in households using a statistical transmission model. We assessed demographic determinants of transmissibility and the infectivity of COVID-19 cases during their incubation period. Findings A total of 195 unrelated close contact groups with 215 primary cases, 134 secondary or tertiary cases and 1964 uninfected close contacts were traced as of Feb. 18, 2020. By identifying households from these groups, we estimated the household SAR to be 12·4% (95% CI 9·8–15·4%) if household contacts are defined as close relatives and 17·1% (95% CI 13·3–21·8%) if household contacts are defined as those living at the same residential address, assuming a mean incubation period of 5 days and a maximum infectious period of 13 days. Compared to the elderly (≥60 years old), the risk of household infection was lower among children (<20 years old, odds ratio [OR]=0·23, 95% CI 0·11–0·46) and among younger adults (20–59 years old, OR=0·64, 95% CI 0·43–0·97). Our results suggest greater infectivity during the incubation period than during the symptomatic period, though the difference was not statistically significant (OR=0·61, 95% CI 0·27–1·38). On average, a…
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Evidence Hub reads this as a cohort study, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence.
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