EXHIBIT 4.

County-level geographic distribution of mRNA vaccine first doses (January 1-July 31, 2021) and booster doses (August 1, 2021-April 30, 2022) among Medicare beneficiaries, overall and by US region

	Overall	Northeast	Midwest	South	West
First dose
No. of counties	3,139	217	1,055	1,420	447
No. of beneficiaries vaccinated across counties
Total	14,448,485	3,075,797	3,620,658	4,938,507	2,813,523
Median	800	5,161	576	876	346
% Pfizer, median	48.38	53.56	49.46	45.45	51.73
Booster dose
No. of counties	3,140	217	1,055	1,422	446
No. of beneficiaries vaccinated across counties
Total	19,151,132	4,167,652	4,178,690	7,105,985	3,698,805
Median	978	6,505	636	1,044	405
% Pfizer, median	42.61	52.45	44.19	39.16	39.99

SOURCE Authors’ analysis of customer data from CVS Health and Walgreens linked to the 100 percent Medicare Enrollment File.

NOTES The number vaccinated across counties represents the total number of Medicare beneficiaries in our study sample who received a first dose or booster dose of COVID-19 mRNA vaccine. The full table that includes interquartile ranges is in appendix exhibit A-1 (see note 11 in text).