Dynamic prioritization of COVID-19 vaccines when social distancing is limited for essential workers

Vaccines were a key intervention to reduce the burden of the COVID-19 pandemic. However, vaccine supply and administration capacity was initially limited. Due to these constraints, it was critical to understand how vaccine deployment could be targeted to minimize the overall burden of disease. In this paper, we solved for optimal dynamic strategies to allocate a limited supply of vaccines over a population differentiated by age and essential worker status that minimizes the number of total deaths, years of life lost, or infections. We found that older essential workers are typically targeted first. However, depending on the objective and alternative model scenarios considered, younger essential workers may be prioritized to control spread or seniors to directly control mortality.

Careful design of a vaccine prioritization strategy across sociodemographic groups is a crucial public policy challenge given that 1) vaccine supply will be constrained for the first several months of the vaccination campaign, 2) there are stark differences in transmission and severity of impacts from infectious disease across groups. We assess the optimal allocation of a limited vaccine supply in the United States across groups differentiated by age and essential worker status, which constrains opportunities for social distancing. We model transmission dynamics using a compartmental model parameterized to capture current understanding of the epidemiological characteristics of COVID-19, including key sources of group heterogeneity (susceptibility, severity, and contact rates). We investigate three alternative policy objectives (minimizing infections, years of life lost, or deaths) and a dynamic strategy that evolves with the population's epidemiological status. We find that this temporal flexibility contributes substantially to public health goals. Older essential workers are typically targeted first. However, depending on the objective, younger essential workers are prioritized to control the spread or seniors to control mortality directly. When the objective is minimizing deaths, relative to an untargeted approach, prioritization averts deaths on a range between 20,000 (when nonpharmaceutical interventions are strong) and 300,000 (when these interventions are weak). We illustrate how optimal prioritization is sensitive to several factors, most notably, vaccine effectiveness and supply, rate of transmission, and the magnitude of initial infections.