Effective vaccination strategies to control COVID-19 outbreak: A modeling study

OBJECTIVES Three years following the start of the COVID-19 pandemic, the World Health Organization (WHO) declared COVID-19 a global health emergency of international concern. As immunity levels in the population acquired through past infections and vaccinations have been decreasing, booster vaccinations have become necessary to control new outbreaks. This study aimed to determine the most suitable vaccination strategy to control the COVID-19 surge. METHODS A mathematical model was developed to simultaneously consider the immunity levels induced by vaccines and infections, and employed to analyze the possibility of future resurgence and control using vaccines and antivirals. RESULTS As of May 11, 2023, a peak in resurgence is predicted to occur around mid-October of the same year if the current epidemic trend continues without additional vaccinations. In the best scenario, the peak number of severely hospitalized patients can be reduced by 43% (480) compared to the scenario without vaccine intervention (849). Depending on the outbreak trends and vaccination strategies, the best timing for vaccination in terms of minimizing the said peak varies from May to August 2023. CONCLUSIONS Our results indicate that if the epidemic continues, the best timing for vaccinations must be earlier than specified by the current plan in Korea. Further monitoring of outbreak trends is crucial for determining the optimal timing of vaccinations to manage future surges.