The Effectiveness of Public Health Interventions Against COVID-19: Lessons from the Singapore Experience

Background: This study conducts a counterfactual analysis, using the case of Singapore, a country fairly successful in suppressing community spread of COVID-19, to explore what the trajectory of COVID-19 infection might have been in Singapore had the government intervention not focused on containment, but rather on mitigation or uninhibited spread. Methods: We developed an SEIR model to estimate the number of COVID-19 infection cases in Singapore and deaths, under different public health intervention compared to the containment interventions implemented in Singapore. Finding: Under the Singapore containment interventions, we would expect a peak in infected cases to occur 3 months from January 23, 2020 [100% confidence range (CR), 2·2 to 4]. The infected cases of COVID-19 over 8·6 months is projected to be 2,488 [1,814 to 4,510]; representing 0·044% of the total population [0·032 to 0·081]. Deaths is estimated to be 25 [9 to 57]. In comparison, a mitigation intervention with 20% quarantine rate, would delay the time to peak infection by an estimated 5·2 months, prolong duration of the infection by 12·4 months, cumulative infected cases 1,388-fold, and deaths 1,371-fold. Likewise, a mitigation intervention with 40% quarantine rate, compared to the Singapore containment intervention could delay the time to peak infection by 7 months, extend the infection surge by 21 months, and increase cumulative infected cases and deaths 727-fold. Finally, a strategy of uninhibited spread would increase the time to peak infection by 2·9 months, duration of infection by 8 months, increase cumulative infected cases 1,863-fold and deaths 1,840-fold. Interpretation: Early public health measures in the context of targeted, aggressive containment — such as swift and effective contact tracing and quarantine – was likely responsible for suppressing the number of COVID-19 infections in Singapore. Funding Statement: The project was funded by the Singapore Ministry of Health’s National Medical Research Council. Declaration of Interests: There is no conflict of interests.