Secondary attack rate of COVID-19 in shared households in Slovakia.

OBJECTIVE: The objective of this study was to estimate the secondary attack rate in unvaccinated members of households of two regions in the Slovak Republic for the period November 2020 ‒ April 2021.

INTRODUCTION: SARS-CoV-2 infection poses a high risk of transmission in close-contact indoor settings, such as households. The household transmissibility of SARS-CoV-2 varies widely across countries.

METHODS: We included 278 households for SARS-CoV-2 transmission analysis. We calculated the secondary attack rate (SAR). We assessed sex, level of disease severity and means of isolation during infection of index cases as determinants of disease transmissibilityRESULTS: The secondary attack rate in 278 households was estimated at 63.7% (95%CI: 58.2‒66.7%). The SARs were different by sex (60.2% in females, 67.5% in males). The highest SAR was observed in the households of asymptomatic cases (77.8%), followed by moderate severity (66.5%), hospital admissions (63.2%) and mild disease (58.2%).

CONCLUSION: We found a high household secondary attack rate in two regions of Slovakia in the period when Alpha variant (B.1.1.7) of SARS-CoV-2 was dominant in the country. The results highlight the importance of monitoring transmission dynamics (Tab. 1, Fig. 1, Ref. 12). Text in PDF www.elis.sk Keywords: COVID-19, secondary attack rate, Slovak Republic, households.