Household transmission of SARS-CoV-2: systematic review and metaanalysis

Background: Public health policies for decreasing the transmission of COVID-19 focus on extradomiciliary measures, but neglect transmission within the home. We aimed to estimate the rate of secondary home attack of SARS-CoV-2. Material and Methods: We conducted a systematic review of observational studies that evaluated home transmission of SARS-CoV-2 published between December 2019 and September 1, 2021 in Medline, Scopus, LILACS, and Google Scholar databases. The definition of household contact referred to any person living in the same house as the index patient. The risk of bias was assessed with a modified version of the Newcastle-Ottawa tool. A meta-analysis was performed with a random-effects model to calculate the household attack rate, subanalysis with sociodemographic, epidemiological variables, and comorbidities, as well as meta-regression. Results: Of 4491 studies found, 44 were included in the analysis. The overall household secondary attack rate was 27.7% (95%CI: 23% -32.7%). Furthermore, it was higher when the index case was symptomatic (28.3%, 95%CI: 8.1% -54.7%) or the contact was an older adult (42.3%, 95%CI: 32% -52.9%). Likewise, the rate was higher when the household contacts had diabetes mellitus (57.4%, 95%CI: 45.2% -69.3%) and arterial hypertension (51.1%, 95%CI: 38% -64.1%). Conclusions: The SARS-CoV-2 household secondary attack rate was 27.7%, being higher when there was an adult index case, older adult contact and contact with diabetes mellitus or hypertension.