Contrasting SARS-CoV-2 Epidemics in Singapore: Cohort Studies in Migrant Workers and the General Population

Abstract

From January 2020, Singapore implemented comprehensive measures to suppress SARS-CoV-2. Community transmission has been limited, although explosive outbreaks have occurred in migrant worker dormitories. We conducted longitudinal SARS-CoV-2 serology studies among 478 residents of a SARS-CoV-2 affected migrant worker dormitory between May and July 2020, and 937 community-dwelling adult Singapore residents with sera collected before September 2019 and in November/December 2020. By end 2020, <2 per 1000 (0.16%, 95% CrI: 0.008% -0.72%) adult residents in the community were infected with SARS-CoV-2, approximately 4 times higher than the national noti ed case incidence. In contrast, in the migrant worker cohort, nearly two-thirds 63.8% (95% CrI: 57.9% -70.3%) had been infected by July 2020; no symptoms were reported in >90% of these infections. SARS-CoV-2 suppression is feasible with rapid implementation of comprehensive control measures. However, the risk of large-scale epidemics in densely-populated environments requires speci c consideration in preparedness planning.

SARS-CoV-2 neutralising antibody activity in a highly vaccinated population: Longitudinal serology studies in Singapore

“…We have previously shown that despite large epidemics in migrant worker dormitories, Singapore experienced very low levels of transmission in the wider community during first year of the pandemic, with <0.2% of the population showing serological evidence of SARS-CoV-2 infection. [1] Transmission gradually increased in 2021, resulting in large epidemic waves associated with the highly-transmissible Delta (B.1.617.2) and Omicron (B.1.1.529) variants in late 2021 and early 2022, and coinciding with the easing of travel restrictions and social management measures. The dramatic rise in the SARS-CoV-2 force of infection associated with the Delta variant is reflected in the high levels of seroconversion among unvaccinated individuals between May/June 2021 and January 2022.…”

“…Methods The characteristics of the two cohorts are described in detail elsewhere. [1] The migrant worker cohort included 541 adult males aged 19-59 years residing in a COVID-19 affected dormitory and who provided blood samples in May 2020 and subsequently after two and six weeks. The community cohort comprised 937 community-dwelling adults aged ≥21 years who provided blood samples for serological analysis in November/December 2020 (Figure 1).…”