COVID-19 Endemic Plan: Impact of Vaccination and Non-pharmaceutical Interventions with Viral Variants and Waning Immunity Using an Agent-Based Simulation

BackgroundsDespite the widespread distribution of SARS-CoV-2 vaccines, the COVID-19 pandemic continues with highly contagious variants and waning immunity. Low disease severity of the Omicron variant gives society hope that the COVID-19 pandemic could end. MethodsWe develop an agent-based simulation to explore the impact of COVID-19 vaccine willingness, booster vaccination schedule, vaccine effectiveness, and non-pharmaceutical interventions (NPIs) on reducing COVID-19 deaths while considering immunity duration and disease severity against the Omicron variant. The model is calibrated to the greater Seattle in year 2020 by observing local epidemic data. The simulation is run to the end of year 2024 to observe long-term effects. ResultsResults show that an NPI policy that maintains low levels of NPIs can reduce mortality by 35.1% compared to fully opening the society. A threshold NPI policy is especially helpful when the disease severity of the Omicron variant is high, or booster vaccines are not scheduled. A periodic booster schedule is needed to achieve the goal of lowering the number of deaths from COVID-19 to the level of influenza and pneumonia. Except for one scenario, 80% or more vaccine willingness is also needed to achieve this goal. ConclusionsWe find that a periodic booster vaccination schedule and mild disease severity of the Omicron variant play a crucial role in reducing deaths by the end of year 2024. If a booster schedule is not planned and the Omicron variant is not mild, NPI policies that limit society from fully opening are required to control the outbreak.