Table 1.

Demographic and Clinical Characteristics of Influenza-Negative Participants Enrolled in the United States Influenza Vaccine Effectiveness Network, 2011–2012 through 2018–2019 Influenza Seasons

	Vaccination Status^a
	Total		Vaccinated
Characteristics	No.	(%)^b	No.	(%)^c
Overall vaccination coverage	45424	100	25063	55
States
Michigan	7713	17	4396	57
Pennsylvania	7925	17	4184	53
Texas	9472	21	4477	47
Washington	11631	26	7214	62
Wisconsin	8683	19	4792	55
Sex
Female	27032	59	15303	57
Male	18391	41	9759	53
Race/ethnicity ^d
White, non-Hispanic	32889	73	18825	57
Black, non-Hispanic	3882	9	1692	44
Hispanic, any race	4275	9	2081	49
Other, non-Hispanic	4234	9	2389	56
Age Group
6 months-4 years^e	8047	18	4967	62
5–12 years	6252	14	2849	46
13–17 years	2831	6	1066	38
18–49 years	15190	33	6824	45
50–64 years	7569	17	4800	63
≥65 years	5535	12	4557	82
Highest education level in household ^e
Some college or less	22686	62	11331	50
College graduate and above	13886	38	8847	64
Comorbidities ^f
None	26623	59	12817	48
1 High-risk medical condition	9696	21	5606	58
2 High-risk medical conditions	3972	9	2675	67
≥3 High-risk medical conditions	5113	11	3965	77
Exposure to cigarette smoke ^g
Yes	7744	83	3409	44
No	37510	17	21575	57
Vaccinated in the prior season
Yes	21183	47	16809	79
No	24241	53	8254	34
Self-reported general health status ^h
Excellent	14591	32	7699	53
Very good	16570	36	9041	55
Good	10993	24	6303	57
Fair/Poor^j	3234	7	2004	62
Body Mass Index (BMI) ⁱ
Underweight (BMI <18.5)	241	1	123	51
Normal (18.5 ≤ BMI < 25)	5724	20	3098	54
Overweight (25 ≤ BMI < 30)	7769	27	4630	60
Obese (30 ≤ BMI < 40)	9824	34	5820	59
Morbidly obese (BMI ≥40)	3272	12	1835	56
Unknown	1463	5	675	46

^a:

Defined as having received ≥1 dose of any current seasonal influenza vaccine prior to clinic visit.

^b:

Percentage refers to column percentage

^c:

Percentage refers to row percentage

^d:

Enrollees were categorized into one of four mutually exclusive racial/ethnic populations: white, black, other race, and Hispanic. Persons identifying as Hispanic might have been of any race. Persons identifying as white, black, or other race were non-Hispanic. Race/ethnicity data were missing for 144 enrollees (<1%).

^e:

Data on education level were only collected from 2013–2014 through 2018–2019 influenza seasons, data missing/refused for 155 enrollees (<1%)

^f:

Comorbidities are defined as ≥1 medical record-documented high-risk code in prior year, as defined by Advisory Committee on Immunization Practices guidance for conditions that increase risk for complications from influenza. High-risk conditions were categorized into groups: asthma, cerebrovascular diseases, chronic obstructive pulmonary diseases (COPD) and other lung diseases, diabetes, cardiovascular diseases, hematologic conditions/blood disorders, liver diseases, neurologic conditions, renal diseases, and immunosuppressive conditions (including rheumatoid arthritis, immune system disorders or immunodeficiency, antineoplastic chemotherapy, HIV, organ transplants).

^g:

Data on exposure to cigarette smoke in household were missing/refused for 170 enrollees.

^h:

“Fair” and “Poor” were grouped together for self-reported health status. Data missing for 36 enrollees (<1%)

^i:

Body mass index was calculated as kg/m² from height and weight recorded in the electronic medical record. Calculated for adults aged ≥18 years only