Resource Allocation for Different Types of Vaccines against COVID-19: Tradeoffs and Synergies between Efficacy and Reach

Kim, D.; Pekgun, P.; Yildirim, I.; Keskinocak, P.

Objective: During the COVID-19 pandemic, multiple vaccine candidates were developed in record time. The primary decision for a vaccine-ordering decision-maker then becomes how to allocate limited resources between different types of vaccines. One may expect that available resources should be favored towards a vaccine with high efficacy if it can be distributed as widely as any other vaccine. However, if a high efficacy vaccine consumes more resources than a vaccine with lower efficacy due to distributional challenges, the decision is no longer trivial as a widespread vaccination is necessary to reach herd immunity. Methods: We adapt a Susceptible-Infected-Recovered-Deceased (SIR-D) model with vaccination and simulate the level of infection attack rate (IAR) under different resource consumption ratios between two vaccine types with different resource allocation decisions. Results: We find that when there are limited resources, allocating resources entirely to a vaccine with high efficacy that becomes available earlier than a vaccine with lower efficacy that becomes available later does not always lead to a lower IAR, particularly if the former can immunize less than a range of 5.9% to 6.4% of the population (with the selected study parameters) before the latter becomes available. Sensitivity analyses show that this result stays robust under different efficacy levels for the higher efficacy vaccine. Conclusions: Our results show that the reach of a vaccine to be distributed widely under limited resources is a key factor to achieve low IAR levels, even though the vaccine may be of higher efficacy and may become available earlier than others. Manufacturing a novel vaccine lacking a fully developed suitable infrastructure for its effective distribution and storage may impact the potential benefits of the immunization program. Understanding the tradeoffs between efficacy and reach is critical for resource allocation decisions between different vaccine types to maximize the improvement in health outcomes.