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

Mutations in SARS-CoV-2 raised concerns about diminishing vaccine effectiveness against COVID-19 caused by particular variants. Even with high initial efficacy, if a vaccine’s 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 the speed of distribution vs. efficacy against infection of multiple vaccines when variants emerge by utilizing a Susceptible-Infected-Recovered-Deceased (SIR-D) model and assessing the level of infection attack rate (IAR). Our 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. Due to supply-chain challenges, the accessibility and distribution of the vaccines have been hindered in many regions, especially in low-income countries, while the second or third wave of the pandemic has occurred due to the variants. Understanding the tradeoffs between speed and efficacy and distributing vaccines that are available as quickly as possible are crucial to eradicate the pandemic before new variants spread.