Vaccine confidence among people who use drugs: A cross-sectional survey

Figures & data

Table 1. Sociodemographic characteristics of study participants, by study location. (N=1,127).

			Total	Las Vegas	Los Angeles	Atlanta
			n (%)	n (%)	n (%)	n (%)
Age (χ^2 = 180; p < .001)
	18 to 30		252 (22.4%)	140 (33.8%)	49 (10.5%)	63 (25.4%)
	31 to 50		590 (52.4%)	243 (58.7%)	212 (45.6%)	135 (54.4%)
	51 or older		285 (25.3%)	31 (7.5%)	204 (43.9%)	50 (20.2%)
Race/Ethnicity (χ^2 = 235; p < .001)
	Hispanic, not multiracial		226 (20.1%)	65 (15.7%)	141 (30.3%)	20 (8.1%)
	Non-Hispanic White alone		478 (42.4%)	267 (64.5%)	107 (23.0%)	104 (41.9%)
	Non-Hispanic Black alone		232 (20.6%)	20 (4.8%)	112 (24.1%)	100 (40.3%)
	Other and/or multiracial		140 (12.4%)	51 (12.3%)	66 (14.2%)	23 (9.3%)
	Don’t know, decline to answer, or missing		51 (4.5%)	11 (2.7%)	39 (8.4%)	1 (0.4%)
Gender (χ^2 = 20; p = .001)
	Male		705 (62.6%)	252 (60.9%)	299 (64.3%)	154 (62.1%)
	Female		406 (36.0%)	162 (39.1%)	157 (33.8%)	87 (35.1%)
	Other		5 (0.4%)	0 (0.0%)	0 (0.0%)	5 (2.0%)
	Decline to answer or missing		11 (1.0%)	0 (0.0%)	9 (1.9%)	2 (0.8%)
Sexual orientation (χ^2 = 57; p < .001)
	Straight		853 (75.7%)	321 (77.5%)	384 (82.6%)	148 (59.7%)
	Gay/Lesbian/Bisexual/Other		248 (22.0%)	87 (21.0%)	65 (14.0%)	96 (38.7%)
	Decline to answer or missing		26 (2.3%)	6 (1.4%)	16 (3.4%)	4 (1.6%)
Education (χ^2 = 19; p = .001)
	Less than high school/GED		244 (21.7%)	67 (16.2%)	128 (27.5%)	49 (19.8%)
	High school/GED		404 (35.8%)	159 (38.4%)	155 (33.3%)	90 (36.3%)
	At least some college/technical		459 (40.7%)	185 (44.7%)	168 (36.1%)	106 (42.7%)
	Decline to answer or missing		20 (1.8%)	3 (0.7%)	14 (3.0%)	3 (1.2%)
Household income (χ^2 = 29; p < .001)
	$20,000 or less		770 (78.5%)	257 (71.2%)	356 (86.6%)	157 (75.1%)
	Greater than $20,000		211 (21.5%)	104 (28.8%)	55 (13.4%)	52 (24.9%)
	Decline to answer or missing		146 (13%)	53 (13%)	54 (12%)	39 (16%)
Primary income source (χ^2 = 197; p < .001)
	Employment (full/part/self)		342 (30.3%)	153 (37.0%)	93 (20.0%)	96 (38.7%)
	Public benefits or disability		423 (37.5%)	85 (20.5%)	293 (63.0%)	45 (18.1%)
	Other		223 (19.8%)	111 (26.8%)	47 (10.1%)	65 (26.2%)
	Decline to answer or missing		139 (12.3%)	65 (15.7%)	32 (6.9%)	42 (16.9%)
Currently homeless or housing insecure (χ^2 = 53; p < .001)
	Yes		680 (60.3%)	199 (48.1%)	322 (69.2%)	159 (64.1%)
	No		376 (33.4%)	195 (47.1%)	119 (25.6%)	62 (25.0%)
	Not sure, decline to answer, or missing		71 (6.3%)	20 (4.8%)	24 (5.2%)	27 (10.9%)
Medical insurance (χ^2 = 330; p < .001)
	Private insurance		48 (4.3%)	21 (5.1%)	17 (3.7%)	10 (4.0%)
	Medicaid/Medicare/Veteran’s/Other, but no private insurance		716 (63.5%)	306 (73.9%)	360 (77.4%)	50 (20.2%)
	No insurance		270 (24.0%)	61 (14.7%)	47 (10.1%)	162 (65.3%)
	Decline to answer, not sure, inconsistent response, or missing		93 (8.3%)	26 (6.3%)	41 (8.8%)	26 (10.5%)
Ever traded sex for goods, a place to stay, money, or drugs/alcohol (χ^2 = 36; p < .001)
	Yes		331 (30.8%)	128 (31.5%)	95 (22.1%)	108 (45.2%)
	No		670 (62.3%)	260 (64.0%)	294 (68.4%)	116 (48.5%)
	Not sure or missing		74 (6.9%)	18 (4.4%)	41 (9.5%)	15 (6.3%)
Intravenous injection drug use in past 6 months (χ^2 = 14; p = .001)
	Yes		765 (67.9%)	331 (80.0%)	267 (57.4%)	167 (67.3%)
	No		150 (13.3%)	43 (10.4%)	75 (16.1%)	32 (12.9%)
	Inconsistent response or missing		212 (18.8%)	40 (9.7%)	123 (26.5%)	49 (19.8%)
Total time incarcerated (χ^2 = 77; p < .001)
	No incarceration history		164 (14.6%)	53 (12.8%)	75 (16.1%)	36 (14.5%)
	Incarcerated, <5 years		613 (54.4%)	277 (66.9%)	186 (40.0%)	150 (60.5%)
	Incarcerated 5+ years		231 (20.5%)	50 (12.1%)	145 (31.2%)	36 (14.5%)
	Missing		119 (10.6%)	34 (8.2%)	59 (12.7%)	26 (10.5%)

Table 2. Vaccine receipt percentages by vaccine confidence class.

	Low confidence	Medium confidence	High confidence
	(EVCI = 0 to 12)	(EVCI = 13 to 20)	(EVCI = 21 to 24)
Vaccine	% receipt	% receipt	% receipt
HepA	42.8%^a	51.9%^b	51.6%^b
HepB	45.7%^a	52.0%^a	48.4%^a
Flu	42.4%^a	55.4%^b	58.4%^b
MMR	53.6%^a	63.3%^b	62.4%^b
Tdap	57.0%^a	66.2%^b	73.0%^b

^a,bVaccine confidence categories with different superscripts differ in vaccination rates for the specified vaccine (p < .05).

Table 3. Odds ratio for increase in likelihood of self-reported vaccine receipt per point of EVCI index.

	Bivariate		Multivariable^†
	Odds ratio	Bivariate	Adjusted odds ratio	Adjusted
Vaccine	(95% CI)	p-value	(95% CI)	p-value
HepA	1.02 (1.00, 1.04)	.022	1.03 (1.00, 1.05)	.018
HepB	1.01 (0.99, 1.03)	.237	1.01 (0.99, 1.03)	.349
Flu	1.05 (1.03, 1.07)	.000	1.05 (1.03, 1.07)	.000
MMR	1.03 (1.01, 1.05)	.009	1.03 (1.00, 1.05)	.021
Tdap	1.04 (1.02, 1.06)	.000	1.04 (1.01, 1.06)	.001

†Multivariable model adjusts for study site, age, race/ethnicity, gender, sexual orientation, education, income, income source, housing insecurity, and insurance.

Table 4. Estimated mean EVCI index scores across sites and sociodemographic factors.

		EVCI score (0-24)
		Mean	(95% CI)
Study Site
Las Vegas		12.4^a	(11.9, 13.0)
Los Angeles		11.7^a,b	(11.1, 12.3)
Atlanta		11.1^b	(10.3, 11.8)
Age
18 to 30		11.7^a	(10.9, 12.4)
31 to 50		11.9^a	(11.4, 12.3)
51 or older		11.9^a	(11.1, 12.6)
Race and ethnicity
Hispanic, not multiracial		11.7^a	(10.8, 12.5)
Non-Hispanic White alone		12.3^a	(11.7, 12.8)
Non-Hispanic Black alone		11.4^a	(10.6, 12.1)
Other and/or Multiracial		11.3^a	(10.3, 12.4)
Gender identity
Male		11.8^a	(11.3, 12.3)
Female		11.8^a	(11.2, 12.4)
Sexual orientation
Straight/Heterosexual		11.8^a	(11.4, 12.2)
Gay/Lesbian/Bisexual/Other		11.8^a	(11.0, 12.5)
Education
Less than high school/GED		11.6^a	(10.8, 12.3)
High school/GED		11.6^a	(11.0, 12.2)
At least some college/technical		12.1^a	(11.6, 12.7)
Household income
$20,000 or less per year		11.7^a	(11.3, 12.1)
Greater than $20,000 per year		12.1^a	(11.4, 12.9)
Primary income source
Employment (full/part/self)		11.5^a	(10.9, 12.1)
Public benefits or disability		12.1^a	(11.5, 12.7)
Other		11.8^a	(11.0, 12.5)
Currently homeless or housing insecure
Yes		11.4^a	(10.9, 11.8)
No		12.6^b	(12.0, 13.2)
Medical insurance
Private insurance		12.7^a	(11.2, 14.3)
Medicare/Medicaid/Veterans’/Other, but no private insurance		11.7^a	(11.2, 12.1)
No insurance		12.0^a	(11.3, 12.7)
Used intravenous injection drugs in last 6 months
Yes		12.0^a	(11.6, 12.4)
No		10.9^b	(10.1, 11.7)
Incarceration history
No incarceration		11.6^a	(10.6, 12.6)
Incarcerated less than 5 years		11.8^a	(11.3, 12.3)
Incarcerated 5 or more years		12.0^a	(11.3, 12.8)

^a,bMeans without a common superscript differ (p < .05).

Table 5. Estimated increase in ECVI from full multivariable linear regression model.

		Adj. Coeff
		(95% CI)	p-Value
Study site
Los Angeles vs Las Vegas		−0.8 (−1.8, 0.2)	.137
Atlanta vs Las Vegas		−1.9 (−3.1, −0.7)	.001
Atlanta vs Los Angeles		−1.1 (−2.4, 0.1)	.065
Age
31 to 50 vs 18 to 30		0.3 (−0.6, 1.2)	.564
51 or older vs 18 to 30		0.2 (−1.1, 1.4)	.775
51 or older vs 31 to 50		−0.1 (−1.1, 1.0)	.878
Race and ethnicity
Non-Hispanic White alone vs Hispanic, not multiracial		0.5 (−0.5, 1.6)	.308
Non-Hispanic Black alone vs Hispanic, not multiracial		0.2 (−1.0, 1.4)	.760
Other and/or multiracial vs Hispanic, not multiracial		−0.2 (−1.5, 1.2)	.793
Non-Hispanic Black alone vs Non-Hispanic White alone		−0.3 (−1.4, 0.7)	.520
Other and/or multiracial vs Non-Hispanic White alone		−0.7 (−1.9, 0.5)	.236
Other and/or multiracial vs Non-Hispanic Black alone		−0.4 (−1.7, 1.0)	.591
Gender identity
Female vs Male		−0.2 (−0.9, 0.6)	.682
Sexual orientation
Gay/Lesbian/Bisexual/Other vs Straight/Heterosexual		0.0 (−0.9, 0.9)	.948
Education
High school/GED vs Less than high school/GED		0.0 (−1.0, 1.0)	.958
At least some college/tech vs Less than high school/GED		0.4 (−0.5, 1.4)	.366
At least some college/tech vs High school/GED		0.4 (−0.4, 1.3)	.315
Household income
Greater than $20,000 vs $20,000 or less		0.1 (−0.9, 1.1)	.831
Primary income source
Public benefits or disability vs Employment (full/part/self)		1.4 (0.4, 2.4)	.006
Other vs Employment (full/part/self)		0.6 (−0.5, 1.6)	.296
Other vs Public benefits or disability		−0.9 (−2.0, 0.2)	.124
Currently homeless or housing insecure
Yes vs No		−1.1 (−2.0, −0.3)	.009
Medical insurance
Public, but no private vs Private insurance		−1.3 (−2.9, 0.3)	.107
No insurance vs Private insurance		0.2 (−1.5, 2.0)	.779
No insurance vs Public, but no private		1.5 (0.5, 2.6)	.004
Used intravenous injection drugs in last 6 months
Yes vs No		0.8 (−0.2, 1.8)	.099
Incarceration history
Incarcerated, <5 years vs No incarceration history		−0.1 (−1.2, 1.0)	.851
Incarcerated, 5+ years vs No incarceration history		0.3 (−1.1, 1.6)	.700
Incarcerated, 5+ years vs Incarcerated, <5 years		0.4 (−0.7, 1.4)	.491