Study: Vaccinating Seniors, Essential Workers First Offers Greatest Public Health Benefit


For the study, the research team modeled COVID-19 transmission rates and the optimal allocation of an initially limited vaccine supply in the United States under a variety of scenarios.

Prioritizing who receives the limited supply of available COVID-19 vaccines saves lives and reduces the spread of infection, according to a study published in the journal PNAS and conducted by researchers at the University of California, Davis.

“Prioritization has benefits because people differ in at least 2 keyways—their risk of infection and the likelihood of serious consequences from infection,” said senior author Michael Springborn, a UC Davis professor in the Department of Environmental Studies and Policy and an economist focused on environmental risk, including infectious disease, in a press release. “We know that front-line essential workers have less capacity to socially distance and thus an elevated risk, while seniors are more seriously impacted by infection. Accounting for this substantially increases the benefits of vaccination.”

For the study, the research team modeled COVID-19 transmission rates and the optimal allocation of an initially limited vaccine supply in the United States under a variety of scenarios. They found that deaths, years of life lost, and infections were between 17% and 44% lower when vaccinations targeted vulnerable populations, particularly seniors and essential workers, rather than an alternative approach in which everyone is equally likely to be vaccinated.

“We also found that in regions where there was a faster increase in infections, and where there is less masking and social distancing occurring, targeting was even more important in avoiding those outcomes,” said lead author Jack Buckner, a PhD candidate in the UC Davis Graduate Group in Ecology, in a press release.

The researchers identified that essential workers should be a vaccination priority along with or shortly after seniors. They also found that policies that target based on both age and essential worker status substantially outperformed those that consider age only.

Previous studies have assumed that a given prioritization strategy remains constant over time, whereas the recent study allows for prioritization to evolve as conditions change, such as when more people in certain groups become vaccinated.

“Once a large proportion of the most vulnerable people or the most likely to be exposed have been vaccinated, it becomes less important who gets it,” Buckner said in a press release.

The study authors note that although the scientific community and public have learned a lot about SARS-CoV-2, there are still many uncertainties to address. This includes how well vaccines impede transmission, how much individuals will relax their protective measures as vaccinations progress, and how durable immunity will be given the rise of new variants.

“The analytic approach put forward in this study to assess the optimal dynamic allocation of vaccines adds to the methodological toolkit with applications beyond the COVID-19 pandemic,” said study author Gerardo Chowell, PhD, a professor of epidemiology and biostatistics at Georgia State University, in a press release.


Prioritizing who gets vaccinated for COVID-19 saves lives. UC Davis. Published April 2, 2021. Accessed April 5, 2021.

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