Modeling the Impact of Emerging COVID-19 Variants: An Extended SEIRD Framework with Vaccine Efficacy Adjustments

The continued surfacing of COVID-19 emphasizes the need for advanced modeling that can help understand the dynamics of the disease due to emerging variants and the effectiveness of strategies for vaccination. This study extends the traditional SEIRD (Susceptible-Exposed-Infectious-Recovered-Deceased) model, considering the effects of a new—more transmissible—COVID-19 variant and varying vaccine efficacy. We incorporate a new compartment of vaccinated but exposed people, accounting for the new variant in increasing transmission intensity. Our model also factors in reduced vaccine efficacy against the variant and terms for vaccination rate and waning immunity. We calibrated this model to data from the World Health Organization (WHO), as well as recent work from the Centers for Disease Control and Prevention (CDC), to provide a robust framework for predicting the spread of the new variant and to assess the impact of vaccination efforts. In this way, the approach offers insight into complex pandemic dynamics, supports public health strategies, and informs policy responses against emerging threats.