Physician preferences for attributes of pediatric combination vaccines in the United States

Figures & data

Table 1. Attributes and levels of vaccine attributes selected to be part of the discrete choice experiment survey.

Attribute	Description	Levels
Vaccine presentation	Combination vaccines can come in the form of a pre-filled syringe that is ready-to-use or in vials that require reconstitution before injection.	Pre-filled syringe Vial that requires reconstitution
Number of injections at a single visit	Infants can receive a different number of injections at a single visit.	2 3 4
Completion rates	Completion of the infant DTaP, IPV, Hib, HepB series can vary, and this may be related to the type of combination vaccine used. In this survey, we define completion of the infant DTaP, IPV, Hib, and HepB series as accumulation of the required number of doses, irrespective of the timing of vaccine administration.	85% 90% 95%
Timeliness rates	On-time administration of the infant DTaP, IPV, Hib, HepB series can vary, and this may be related to the type of combination vaccine used. In this survey, we define on-time administration as receiving all doses within 30 days of the recommended age.	80% 90% 100%
Years that the vaccine has been available for routine use	Individual components of combination vaccines have been available for many years. However, combination vaccines become available at different times.	Less than 1 year Between 1 and 3 years More than 3 years

Figure 1. Relative importance of attributes. Note: Relative importance is the largest absolute difference in strength of preferences for a given change in levels of that attribute, divided by the sum of those differences across all attributes.

Table 2. Physician characteristics.

Variable	Statistic or category	Total (N = 400)
Specialty, N (%)	Family physician	25.0%
	Pediatrician	75.0%
Age (years)*	Mean (SD)	50.40 (10.13)
	Median (Q1–Q3)	50.0 (42.0–58.0)
	Range	30.0–84.0
Sex, N (%)*	Female	52.5%
	Male	45.0%
	Other/prefer not to answer	2.5%
	Prefer not to answer	1.5%
Practice location, N (%)*	Urban	41.5%
	Suburban	42.8%
	Rural	15.8%
Practice region, N (%)*	Midwest	22.5%
	Northeast	21.0%
	South	33.0%
	West	23.5%
Practice type, N (%)	Solo/duo practice	40.5%
	Group practice	58.8%
	Other	0.8%
Practice affiliation, N (%)	Hospital	45.5%
	Clinic	57.3%
	Federally qualified health center	21.3%
	Academic health center	6.0%
	Integrated delivery network	8.8%
	Other	9.0%
Number of years in practice since completing residency or fellowship**	N	399
	Mean (SD)	19.69 (9.34)
	Median (Q1–Q3)	19.0 (12.0–25.0)
	Range	2.0–50.0
Average number of infants (0–12 months) seen in a month, not accounting for decreases due to the COVID-19 pandemic, N (%)	1–60 infants per month	36.0%
	61–120 infants per month	35.8%
	More than 120 infants per month	28.3%

*Soft quotas were employed for age, sex, region, and practice location. Quotas were relaxed once minimums were met.

**One physician skipped this question and was excluded from the analysis for this item.

Table 3. Physician preferences for vaccine attributes.

Variable	Odds Ratio (OR)	95% CI
Number of injections at a single visit
Four injections at a single visit	Reference	Reference
Three injections at a single visit	1.97*	(1.76, 2.20)
Two injections at a single visit	3.12*	(2.63, 3.70)
Timeliness rates (within 30 days of recommended age)
80%	Reference	Reference
90%	1.23*	(1.09, 1.37)
100%	1.81*	(1.59, 2.05)
Completion rates
85%	Reference	Reference
90%	1.44*	(1.30, 1.61)
95%	1.74*	(1.61, 2.00)
Vaccine presentation
Vial	Reference	Reference
Pre-filled syringe	1.51*	(1.36, 1.69)
Years vaccine has been available for routine use
Less than 1 year	Reference	Reference
Between 1 and 3 years	1.30*	(1.11, 1.47)
More than 3 years	1.20*	(1.05, 1.38)

CI: confidence interval; OR: odds ratio.

CIs were estimated using the Delta method.

*Statistically significant at p < .05.

Table 4. Preference strength of attribute levels in relation to preference strength of moving from four or three injections to two injections per visit.

Variable	Compared to importance of reducing the number of injections from 3 to 2 injections in a single visit. Odds ratio (95% CI)	Compared to importance of reducing the number of injections from 4 to 2 injections in a single visit. Odds ratio (95% CI)
Number of injections at a single visit
Reducing number of injections from 4 to 2 in a single visit	1.68 (1.40, 1.96)	Reference
Reducing number of injections from 3 to 2 in a single visit	Reference	0.60 (0.51, 0.68)
Timeliness rates (within 30 days of recommended age)
Improving timelines rates from 80% to 90%	0.30 (0.13, 0.47)	0.18 (0.07, 0.29)
Improving timelines rates from 80% to 100%	0.88 (0.66, 1.10)	0.52 (0.38, 0.67)
Completion rates
Improving completion rates from 85% to 90%	0.54 (0.36, 0.72)	0.32 (0.21, 0.44)
Improving completion rates from 85% to 95%	0.82 (0.58, 1.06)	0.49 (0.34, 0.64)
Vaccine presentation
Preference for pre-filled syringe vs. a vial that requires re-constitution	0.61 (0.43, 0.80)	0.37 (0.26, 0.48)
Years since vaccine has been available for routine use
Preference for vaccine that has been on the market 1–3 years vs. <1 year	0.39 (0.20, 0.57)	0.23 (0.11, 0.35)
Preference for vaccine that has been on the market more than 3 years vs. <1 year	0.27 (0.07, 0.47)	0.16 (0.03, 0.30)

CI: confidence interval.

Data availability statement

The data that supports the findings of this study are available from the corresponding author, SS, upon reasonable request.