Modeling and simulation of periodic lockdowns on COVID-19 dynamics using an adaptive SIRV model with daily-varying rates

We introduce a model for analyzing periodic short-term COVID-19 lockdowns featuring short, alternating periods of W working days and L lockdown days with a weekly cycle: W+L=7. A modified adaptive SIR epidemic model with vaccination (A-SIRV) with a smooth damping function is used to account for periodic suppression of the transmission rate. We use real-world COVID-19 data from Indonesia, United States, Singapore, and Israel to estimate the non-constant transmission and recovery rates using the Method of Variational Imbedding (MVI). The calculated rates reveal that the results of the simulation using A-SIRV models without a damping function approximate the real-world data accurately enough, with low RMSE and MAE values and high values for the coefficient of determination. We also validate the transmission rates with phases of Delta and Omicron variants and obtain agreeable results. We then simulate various scenarios of periodic short-term lockdown using the damped A-SIRV model, finding that implementing five working days and two lockdown days throughout the entire simulation period is sufficient for consistently flattening the number of active cases in the models for Indonesia and United States. However, for the Singapore and Israel models, the use of five working days and two lockdown days only flattens the number of active cases for several years before a blow-up, an extremely high peak of active cases, appears despite the periodic lockdown remaining in place. We then perform additional numerical simulations for Singapore and Israel models and find that the sudden extreme peak can be suppressed by three scenarios: increasing the share of vaccination to the susceptibles, reducing the number of working days per week to three, or using a dynamic policy of five working days per week followed by a policy shift to only two working days per week when sudden extreme peaks start to form. Our study finds that preventive vaccination should be emphasized while allowing partial economic activity during periodic lockdowns.