Projecting the impact of behaviour and isolation interventions and super spreader events from mass gatherings and international travel on Malaysia's COVID-19 epidemic trajectories using an augmented SEIR model

Ayub, A. J.; Ho, G. W. S.; Mohd Hanafiah, K.

Background: Various levels of lockdown implemented to contain the rapid spread of COVID-19 are not long-term solutions due to socioeconomic implications. Methods: To inform safe reopening, we used an augmented SEIR model to project the impact of 1) interventions and potential new epidemic trajectories arising from super spreader (SS) events and/or international travel and 2) re-introducing strong behavioural interventions on resurgence trajectories. Results: Our model suggests that 50% behaviour intervention effectiveness (BIE) (from enforced social distancing during lockdown, early in the epidemic), along with 50% isolation intervention effectiveness (IIE) (from increased testing and isolating infected individuals) was achieved during lockdown, which curbed COVID-19 transmission in Malaysia. Post-lockdown, BIE plays a minimal role if IIE reaches or exceeds 46.9% when other variables are held constant. At IIE of 30% and BIE of 21.3%, SS events of 5,000 active cases risks COVID-19 resurgence, with 4-year projected 12.9mn cumulative cases and 1.1mn deaths. Earlier action to increase BIE to 50% on day 98 compared to day 111, prevented an additional 21,401 recovered cases and 257 deaths. Conclusion: Until a safe and effective vaccine is widely available, the risk of COVID-19 resurgence from large SS events warrants caution in decisions to allow for mass gatherings and regular international travel.