Table 1.

Characteristics of the three study cohorts: no influenza vaccination, influenza vaccination, and vaccination other than influenza.

Characteristics	No influenza vaccination	Percent	Influenza vaccination	Percent	Vaccination other than influenza	Percent
N	42,629,666		13,038,311		1,783,969
Age 75 and older	17,909,748	42	5,568,818	43	671,574	38
Male	19,042,518	45	5,636,245	43	739,562	41
Risk factors
Asthma	91,734	0.22	31,753	0.24	5052	0.28
Chronic kidney disease with dialysis	43,809	0.10	1787	0.014	888	0.050
Chronic lung disease	1,520,026	3.6	365,723	2.8	50,698	2.8
Diabetes mellitus	4,620,287	11	1,165,787	8.9	175,659	9.8
Hemoglobin disorder	17,624	0.041	4285	0.033	776	0.043
Immunocompromised	214,861	0.50	59,518	0.46	9384	0.53
Liver disease	158,425	0.37	32,516	0.25	5973	0.33
Serious heart condition	3,528,349	8.3	891,346	6.8	122,178	6.8
Severe obesity	1,511,601	3.5	423,755	3.3	67,534	3.8
Other vaccination1	34,669,841	81	8,004,874	61	Not applicable
Vaccine with adjuvant	Not applicable		3,740,784	29	Not applicable
Outcome
COVID-19 infection	532,550	1.2	117,467	0.90	17,472	0.98
Severe COVID-19 illness	8540	0.020	1302	0.010	223	0.013

¹Other vaccines: herpes zoster, pneumococcal pneumonia, tetanus, and hepatitis A.