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

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.