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Publication Briefs

VA Researchers Develop Model to Estimate Risk of COVID-19 Related Deaths among Veterans for Use in Prioritizing Vaccine

Prioritizing persons for vaccination according to their risk of COVID-19 related death would minimize the number of these deaths that would occur in the time it takes to vaccinate a large enough proportion of the US population to achieve herd immunity. This study sought to develop a model to estimate the risk of COVID-19 related death in the general population to aid vaccination prioritization. Investigators used electronic health record data developed from the COVID-19 Shared Data Resource to identify Veterans in VA care (7.6 million) during the study observation period (May 21, 2020 to November 2, 2020). Investigators then developed a logistic regression model – called COVIDVax [available at COVID-19 Vaccine Model (] – to see if it could accurately predict the risk of COVID-19 related death. In estimating the risk, COVIDVax used the following 10 patient characteristics: sex, age, race, ethnicity, body mass index (BMI), Charlson Comorbidity Index (CCI), diabetes, chronic kidney disease, congestive heart failure, and the Care Assessment Need (CAN) score. In determining the efficacy of COVIDVax, the main outcome was COVID-19 related death, defined as death within 30 days of testing positive.


  • Prioritizing vaccination based on the COVIDVax model was estimated to prevent a large proportion of deaths expected to occur during vaccine rollout until sufficient herd immunity is achieved.
  • Assuming vaccination is 90% effective at preventing COVID-19 related death, using COVIDVax to prioritize vaccination was estimated to prevent 64% of deaths that would occur by the time 50% of VA enrollees are vaccinated, significantly higher than prioritizing vaccination based on age (46%) or the CDC phases of vaccine allocation (41%).


  • Healthcare systems, such as VA, that have the capability to do so should consider implementing COVIDVax. Further, the CDC Advisory Committee on Immunization Practices (ACIP) should consider modification or sub-stratification of their proposed allocation phases to better capture risk of COVID-19-related mortality. Even under conditions when vaccine supply is not limited, the model can help target individuals who might not yet be vaccinated but are at highest risk from COVID.


  • Study calculations under-estimate the overall vaccination benefit as they do not account for the beneficial impacts on those unvaccinated through lowering transmission.
  • To determine the extent to which the COVIDVax model results are generalizable to non-Veteran populations, the model will need to be externally validated.

This study was partly funded by CSR&D. Drs. Ioannou, Green, and Fan are part of HSR&D’s Center of Innovation for Veteran-Centered & Value-Driven Care in Seattle, WA and Denver CO, and all authors are part of the VA Puget Sound Health Care System.

Ioannou G, Green P, Fan V, et al. Development of COVIDVax Model to Estimate the Risk of SARS-CoV-2–Related Death Among 7.6 Million US Veterans for Use in Vaccination Prioritization. JAMA Network Open. April 6, 2021;4(4):e214347.

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What are HSR Publication Briefs?

HSR requires notification by HSR-funded investigators about all articles accepted for publication. These journal articles are reviewed by HSR and publication briefs or summaries are written for a select number of articles that are then forwarded to VHA Central Office leadership to keep them informed about important findings or information. Articles to be summarized are selected by HSR based on timeliness of the findings, interest of leadership, or potential impact on the organization. Publication briefs are written for only a small number of HSR published articles. Visit the HSR citations database for a complete listing of HSR articles and presentations.

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