Preferences for herpes zoster vaccination among adults aged 50 years and older in the United States: results from a discrete choice experiment

Figures & data

Table 1. Attributes and levels for the DCE

Attribute	Levels for experimentally designed vaccines		Levels for the no vaccine option
Number of HZ cases prevented in the next 5 years^a	Low Baseline Risk Prevents 10 out of 33 cases in 1,000 people (a 30% reduction) Prevents 17 out of 33 cases in 1,000 people (a 50% reduction) Prevents 32 out of 33 cases in 1,000 people (a 97% reduction)	High Baseline Risk Prevents 16 out of 54 cases in 1,000 people (a 30% reduction) Prevents 27 out of 54 cases in 1,000 people (a 50% reduction) Prevents 53 out of 54 cases in 1,000 people (a 97% reduction)	Prevents 0 out of [33,54] cases in 1,000 people (a 0% reduction)
Number of years until you need to get the vaccine again	2 years 12 years 20 years		None
Where you can go to get the vaccine	Doctor’s office only Doctor’s office or pharmacy		None
Number of vaccine doses	1 dose 2 doses		None
Number of days with FLS^b	No days 1 day 3 days		No days
Severity of ISR^c	None Mild Moderate-to-severe		None
Total OOP cost for all vaccine doses	$0 for all doses $15–$25 for all doses $280–$300 for all doses		$0 for all doses

^aRespondents were presented with different baseline risks of contracting HZ in the next 5 years based on their age. Respondents aged 50–64 years (i.e. the commercial health plan population) were shown a baseline HZ risk of 33 out of 1,000 people in the next 5 years. Respondents aged ≥ 65 years (i.e. the Medicare population) were shown a baseline HZ risk of 54 out of 1,000 people. Therefore, VE was communicated to respondents as the percent reduction in the number of HZ cases from baseline. The percentage point change in VE remained the same between the two versions.

^bLevels of FLS were labeled differently depending on the number of vaccine doses shown in each profile. No days, 1 day, and 3 days were the labels when the number of vaccine doses was one; however, for vaccine with 2 doses, the text ‘2 days total’ was added in parentheses after 1 day and ‘6 days total’ was added in parentheses after 3 days.

^cLevels of severity of ISR were labeled differently depending on the number of vaccine doses shown in each profile. When the level for the number of vaccine doses attribute was one, the labels for the ISR attribute were: no reactions, 1 mild reaction, and 1 moderate-to-severe reaction. When the level for the number of vaccine doses attribute was two, the labels for the ISR were no reactions, 2 mild reactions, and 2 moderate-to-severe reactions.

Abbreviations: DCE, discrete choice experiment; FLS, flu-like symptoms; HZ, herpes zoster; ISR, injection-site reactions; OOP, out-of-pocket; VE, vaccine effectiveness.

Figure 1. Sample DCE question from the high-baseline-risk (aged ≥ 65 years, Medicare population) version

Notes: a) Each respondent answered eight DCE questions; the vaccine profiles and pairs were determined by an experimental design (as described in the text). b) ‘Number of HZ cases prevented in the next 5 years’: Risk pictograms were used to describe vaccine effectiveness. There are 1,000 dots in each risk pictogram. Each dot represents one person who has received an HZ vaccine. The gray dots show how many people will not get HZ in the next five years. The blue dots show how many people will get HZ in the next five years. The orange dots show the number of people that would have gotten HZ without the vaccine, i.e. the number of HZ cases prevented by the vaccine. Abbreviations: DCE, discrete choice experiment, FLS, flu-like symptoms; HZ, herpes zoster; ISR, injection-site reactions; OOP, out-of-pocket.

Table 2. Respondent characteristics (N = 1,454)

Characteristic	Responses, n (%)
Aged 50–64 years	712 (49.0)
Aged ≥ 65 years	742 (51.0)
Female	852 (58.6)
Highest level of education^a
Less than high school/some high school but no degree	26 (1.8)
High school or equivalent	254 (17.5)
Some college but no degree/technical school/associate’s degree (2-year college degree)	580 (39.9)
4-year college degree	319 (21.9)
Some graduate school but no degree	58 (4.0)
Graduate or professional degree	217 (14.9)
Employment status^a
Employed full-time	278 (19.1)
Employed part-time	115 (7.9)
Self-employed/homemaker	149 (10.2)
Student	3 (0.2)
Retired	743 (51.1)
Disabled/unable to work	106 (7.3)
Unemployed	60 (4.1)
Race or ethnicity^b
American Indian or Alaska Native	17 (1.2)
Asian Indian	2 (0.1)
Black or African-American	366 (25.2)
Chinese	8 (0.6)
Filipino	2 (0.1)
Japanese	7 (0.5)
Korean	2 (0.1)
Native Hawaiian	2 (0.1)
Other Asian	4 (0.3)
Other Pacific Islander (for example: Fijian, Tongan, etc.)	0
White	1,046 (71.9)
Other	21 (1.4)
I prefer not to say	7 (0.5)
Had influenza vaccination in the past 2 years (since 2016)	728 (50.1)
Health insurance^b
I do not have health insurance	63 (4.3)
Private insurance that I pay for myself (including Medicare supplemental)	235 (16.2)
Private insurance that my employer or my spouse’s employer pays for	357 (24.6)
Medicaid	195 (13.4)
Medicare	749 (51.5)
Veterans’ Health Insurance	89 (6.1)
Other	54 (3.7)
Don’t know or not sure	8 (0.6)
Total household income before tax and other deductions in 2017^a
Less than $25,000	301 (20.7)
$25,000 to $49,999	405 (27.9)
$50,000 to $74,999	259 (17.8)
$75,000 to $99,999	170 (11.7)
$100,000 to $149,999	142 (9.8)
$150,000 to $199,999	58 (4.0)
$200,000 or more	40 (2.8)
Do not know or not sure	2 (0.1)
Prefer not to answer	77 (5.3)
Among respondents who identify as Black or African-American (n = 366)
Ethnic background/origin^b
Africa	175 (47.8)
The Caribbean	34 (9.3)
Central, Latin, or South America	7 (1.9)
Don’t know or not sure	153 (41.8)
I prefer not to say	12 (3.3)

^aSums of percentages may not sum to 100.0% due to rounding.

^bThe percentages may sum to more than 100% because respondents had the option to select more than one response category.

Figure 2. Preference weights and conditional relative importance of attributes of HZ vaccines for the full sample (N = 1,454)

Notes: a) The dark dots in the figure represent the point estimates of relative mean preference weight for attribute levels. b) The vertical bars surrounding each mean preference weight denote the 95%CI about the point estimate. c) The asterisks indicate the segments or differences in attribute levels that were significant at the 95%CI. d) The blue rectangles and associated numbers indicate the conditional relative importance of HZ vaccine attributes. With the exception of ‘where you can go to get the vaccine’, the conditional relative importance weights for all other vaccine attributes were statistically significantly different from zero. In addition, the differences between the conditional relative importance weights for each attribute were statistically significantly different from one another at the 95%CI, with the exception of the following: duration of effectiveness and FLS, duration of effectiveness and ISR, FLS and ISR. Abbreviations: CI, confidence interval; FLS, flu-like symptoms; HZ, herpes zoster; ISR, injection-site reactions; OOP, out-of-pocket.

Figure 3. Conditional relative importance weights of attributes of HZ vaccines for African-American subgroups

Note: The vertical bars surrounding each mean preference weight denote the 95%CI about the point estimate. The asterisk indicates that the conditional relative attribute importance was statistically significantly different between subgroups at the 95%CI. Abbreviations: CI, confidence interval; FLS, flu-like symptoms; HZ, herpes zoster; ISR, injection-site reactions; OOP, out-of-pocket.

Figure 4. Conditional relative importance weights of attributes of HZ vaccines for latent groups within the African-American subgroup (N = 366)

Note: The vertical bars surrounding each mean preference weight denote the 95%CI about the point estimate. Abbreviations: CI, confidence interval; FLS, flu-like symptoms; HZ, herpes zoster; ISR, injection-site reactions; OOP, out-of-pocket.

Figure 5. Predicted choice probabilities or uptake for HZ vaccines with different attributes among latent groups within the African-American subgroup (N = 366)

Note: All other vaccine characteristics are held constant for these comparisons. Abbreviations: FLS, flu-like symptoms; HZ, herpes zoster; ISR, injection-site reactions; OOP, out-of-pocket; vs, versus.

Table 3. Frequency of responses to the second dose compliance questions for the full sample (N = 1,454)

Question and response	First-dose vaccine			Average across all sets (%)
	Set 1, n (%)	Set 2, n (%)	Set 3, n (%)
Given your experience with the first dose, would you get the second dose if it costs $8–$13?	N = 1,454	N = 1,454	N = 1,454
Definitely yes or probably yes	1,116 (76.8)	1,053 (72.4)	1,127 (77.5)	75.5
Definitely no or probably no	338 (23.2)	401 (27.6)	327 (22.5)	24.4
Would you get the second dose if it costs $140–$150?	n = 1,116	n = 1,053	n = 1,127
Definitely yes or probably yes	572 (51.3)	545 (51.8)	571 (50.7)	51.2
Definitely no or probably no	544 (48.7)	508 (48.2)	556 (49.3)	48.8
Would you get the second dose if it costs $0?	n = 338	n = 401	n = 327
Definitely yes or probably yes	64 (18.9)	79 (19.7)	61 (18.7)	19.1
Definitely no or probably no	274 (81.1)	322 (80.3)	266 (81.3)	80.9

Notes:

a) The hypothetical vaccine profiles in these questions were described as requiring two doses, which were meant to be given 12 months apart, 97% effective, and lasting for 12 years.

b) The FLS and ISR varied. The results in the table combine responses across scenarios describing varying levels of FLS and ISR: 9 combinations i.e. 3 levels of FLS (0, 1, or 3 days with FLS) × 3 levels of ISR (none, mild, moderate-to-severe). Each of these nine possible combinations of FLS and ISR were grouped into sets of three different first-dose vaccine scenarios. Each of the nine possible combination appeared an equal number of times and was combined with other combinations an equal number of times across the three pairs of second-dose compliance questions. This led to 84 sets, where each set included three combinations of FLS and ISR. Each respondent was randomly assigned to one set.

c) Sums of percentages may not sum to 100.0% due to rounding.

Abbreviations: FLS, flu-like symptoms; ISR, injection-site reactions.