SARS-CoV-2 transmission among high-risk contacts
| 3 November 2020 | Singapore’s comprehensive approach to COVID-19 control, much of which was prepared following the 2003 SARS epidemic, is likely to have contributed to the low secondary attack rate among household and non-household contacts during the study period.
Ng OT, Marimuthu K, Koh V, et al. SARS-CoV-2 seroprevalence and transmission risk factors among high-risk close contacts: a retrospective cohort study. Lancet Infect Dis 2020, published 2 November. Full-text: https://doi.org/10.1016/S1473-3099(20)30833-1
Excellent retrospective cohort study by Vernon Lee, Oon Tek Ng and colleagues Between Jan 23 and April 3, 2020, the authors identified 7,518 close contacts (1779 [23%] household contacts, 2231 [30%] work contacts, and 3508 [47%] social contacts) linked to 1114 PCR-confirmed index cases.
The secondary clinical attack rate:
Household contacts: 5.9% (95% CI 4.9–7.1).
Particular risk factors:
- Sharing a bedroom (multivariable odds ratio [OR] 5.38)
- Being spoken to by an index case for 30 min or longer (7.86)
Non-household contact: Work contacts, 1.3% (0.9–1.9); social contacts, 1.3% (1.0–1.7).
Particular risk factors:
- Exposure to more than one case (3.92)
- Being spoken to by an index case for 30 min or longer (2.67)
- Sharing a vehicle with an index case (3.07).
Among both household and non-household contacts, indirect contact, meal sharing, and lavatory co-usage were not independently associated with SARS-CoV-2 transmission.
