• Chen-Yang Hsu, Jann-Tay Wang, Kuo-Chin Huang, Antoria Chiao-Hsin Fan, Yen-Po Yeh, and ChenSam Li-ShengSLSchool of Oral Hygiene, College of Oral Medicine, Taipei Medical University, Taipei, Taiwan; Research Center of Cancer Translational Medicine, Taipei Medical University, Taipei, Taiwan. Electronic address: samchen@tmu.edu.tw..
• Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan; Daichung Hospital, Miaoli, Taiwan.
• J Formos Med Assoc. 2021 Jun 1; 120 Suppl 1: S38S45S38-S45.

BackgroundHousehold transmission is responsible for the subsequent outbreak of community-acquired COVID-19. The aim of this study was to elucidate the household transmission mode and to further estimate effective and basic reproductive number with and without non-pharmaceutical interventions (NPIs).MethodsA total of 26 households with 39 family clusters between January, 2020 and February, 2021 in Taiwan were enrolled for analysis. The Becker's chain binomial model was used to analyze the probabilities of being infected and escaping from SARS-COV-2 before and after January 1st, 2021, which were further converted to estimating basic reproductive numbers in the absence of NPIs. The likelihood of leading to the subsequent community-acquired outbreak given NPIs was further assessed.ResultsThe secondary attack rate was 46.2%. Given the saturated Greenwood model selected as the best fitted model, the probability of being infected and escaping from COVID-19 within household was estimated as 44.4% (95% CI: 5.0%-53.7%) and 55.7% (95% CI: 46.3%-65.0%), respectively. In the second period of early 2021, the infected probability was increased to 58.3% (95% CI: 12.7%-90.0%) and the escape probability was lowered to 41.7% (95% CI: 0.0%-86.9%). The corresponding basic reproductive numbers (R0) increased from 4.29 in the first period to 6.73 in the second period without NPIs. However, none of subsequent community-acquired outbreak was noted in Taiwan given very effective NPIs in both periods.ConclusionThe proposed method and results are useful for designing household-specific containment measures and NPIs to stamp out a large-scale community-acquired outbreak as demonstrated in Taiwan.Copyright © 2021. Published by Elsevier B.V.

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