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. Author manuscript; available in PMC: 2024 Jun 4.
Published in final edited form as: Health Aff (Millwood). 2024 May;43(5):659–665. doi: 10.1377/hlthaff.2023.00813

Exhibit 2. Predicted probability of Pfizer-BioNTech for booster doses of mRNA vaccine among Medicare beneficiaries, August 1, 2021–April 30, 2022.

Exhibit 2

SOURCE Authors’ analysis of customer data from CVS Health and Walgreens linked to the 100 percent Medicare Enrollment File. NOTES Statistical interaction product terms between month of vaccination and level of urbanicity were specified in the regression model to visualize changes in the predicted probability of receiving the Pfizer-BioNTech vaccine over time within levels of urbanicity. The figure shows 95% confidence intervals, but the large sample size limits the value of conventional hypothesis testing. The rural-urban classification categories are classifications of the National Center for Health Statistics. Large central metro is the most urban, followed by large fringe metro, medium metro, small metro, micropolitan, and noncore, with noncore counties being the most rural. The increase in the predicted probability of Pfizer-BioNTech booster doses in September 2021 likely corresponds to when the Food and Drug Administration authorized the booster dose of Pfizer-BioNTech vaccine.