The Balancing Role of Distribution Speed against Varying Efficacy Levels of COVID-19 Vaccines under Variants

ObjectiveRecent mutations in SARS-CoV-2 raised concerns about diminishing vaccine effectiveness against COVID-19 caused by particular variants. Even with a high initial efficacy, if a vaccines efficacy drops significantly against variants, or if it cannot be distributed quickly, it is uncertain whether the vaccine can provide better health outcomes than other vaccines. Hence, we evaluated the trade-offs between speed of distribution vs. efficacy of multiple vaccines when variants emerge. MethodsWe utilized a Susceptible-Infected-Recovered-Deceased (SIR-D) model to simulate the impact of immunization using different vaccines with varying efficacies and assessed the level of infection attack rate (IAR) under different speeds of vaccine distribution. ResultsWe found that a vaccine with low efficacy both before and after variants may outperform a vaccine with high efficacy if the former can be distributed more quickly. Particularly, a vaccine with 65% and 60% efficacy before and after the variants, respectively, can outperform a vaccine with 95% and 90% efficacy, if its distribution is 46% to 48% faster (with the selected study parameters). ConclusionsOur results show that speed is a key factor to a successful immunization strategy to control the COVID-19 pandemic even when the emerging variants may reduce the efficacy of a vaccine.