International adaptation and validation of the Pro-VC-Be: measuring the psychosocial determinants of vaccine confidence in healthcare professionals in European countries

Figures & data

Table 1. Characteristics of HCPs^a, by country (n = 2,748).

	All (n = 2748)	France (n = 1213)	Finland (n = 375)	Portugal (n = 557)	Germany (n = 603)	χ^2 p-value
What is your gender identity? (Please select all that apply)						<.0001
Male	40.3	44.6	21.3	19.9	62.2
Female	59.7	55.4	78.7	8.1	37.8
Age category						<.0001
Under 40	32.8	32.6	14.1	66.4	13.9
40–49	22.9	26.8	21.3	19.4	19.1
50 and over	44.3	40.6	64.5	14.2	67.0
What is your profession?						<0.0001
General practitioner	77.5	100.0	69.9	44.0	68.0
Pediatrician	18.3	0.0	30.1	56.0	13.1
Gynecologist	4.2	0.0	0.0	0.0	18.9

Abbreviations. HCPs: healthcare professionals; GPs: general practitioners; UK: United Kingdom.

^aFor information, of the 118/135 HCPs from the UK with no missing data: 26 (22%) were male, 92 (78%) were female; 32 (27%) were under 40, 27 (23%) were 40–49, 59 (50%) were 50 or over; 16 (14%) were GPs, 100 (85%) were nurses, and 2 (<2%) were pediatricians.

Figure 1. Multigroup confirmatory factor analysis^a with scalar invariance: structure and factor loadings (n = 2,748).Abbreviations. resp. = responsibility. RMSEA = root mean square error of approximation; CFI = comparative fit index; TLI = Tucker-Lewis index; SRMR = standardized root mean square residual. ^aFactors were allowed to correlate. All item intercepts and factor loadings were set to be held equal across countries, and the metrics of the factors were defined by fixing their variances to one in one country while freely estimated in the others. *P ≤ 0.05 **P ≤ 0.01 ***P ≤ 0.001. Models with CFI ≥0.90, TLI ≥0.90, RMSEA <0.06, and SRMR <0.08 were considered to fit reasonably or well [39].

Table 2. Test of measurement invariance of the I-Pro-VC-Be: comparison of configural, metric, and scalar invariance models (n = 2,748; 33 items^a.).

				Comparison to configural model			Comparison to metric model
	χ^2 value	Df	Scaling correction factor for MLR	Robust χ^2 difference^b	df difference	P-value	Robust χ^2 difference^b	df difference	P-value	RMSEA (90% CI)	CFI	TLI	SRMR
Configural	4009.6	1800	1.22							.042 (.041–.044)	0.93	0.91	0.05
Metric	3961.7	1869	1.30	75.7	69	0.27				.040 (.039–.042)	0.93	0.92	0.05
Scalar	3994.2	1938	1.29	116.6	138	0.91	0.13	69	1.00	.039 (.038–.041)	0.93	0.93	0.05

Abbreviations. I-Pro-VC-Be: International Professionals’ Vaccine Confidence and Behaviors; Df: degrees of freedom; MLR: maximum likelihood with robust standard errors; RMSEA (90% CI): root mean square error of approximation with 90% confidence interval; CFI: comparative fit index; TLI: Tucker-Lewis index; SRMR: standardized root mean square residual; MG-CFA: multigroup confirmatory factor analysis.

^aThe MG-CFA structure included 10 factors allowed to correlate: safety (4 items after exclusion of the item regarding COVID-19 vaccines), complacency (3 items), benefit/risk balance (5 items), collective responsibility (2 items), trust in authorities (3 items), commitment to vaccination (3 items), self-efficacy (4 items), openness to patients (3 items), perceived constraints (3 items), and reluctant trust (3 items).

^bRobust ${\chi }^2$ proposed in [37; 38] for testing a restricted model against a less restricted one when estimating models using maximum likelihood with robust standard errors.

Models with CFI ≥ 0.90, TLI ≥ 0.90, RMSEA < 0.06, and SRMR < 0.08 were considered to fit reasonably or well [39].

Lecture: The configural model showed good fit (RMSEA = .042 (.041–.044); CFI = 0.93, TLI = 0.91, SRMR = 0.05). The comparison of the metric to the configural model, based on robust ${\chi }^2$ difference at alpha = 0.05, indicated no significant difference between these two models (P = 0.27), implying invariance between the two models and thus metric invariance. The comparison of the scalar to the metric model, based on robust chi-square difference, indicated no significant difference (P = 1.00), implying invariance between the two models and thus scalar invariance.

Table 3. Correlations of the factors from the multigroup confirmatory factor analysis^a with scalar invariance, by country (n = 2,748).

	S	C	BRB	CR	TA	CV	SE	OP	PC	RT
France
S	1.00
C	−0.17	1.00
BRB	0.34	−0.49	1.00
CR	0.24	−0.26	0.40	1.00
TA	0.27	−0.30	0.42	0.33	1.00
CV	0.19	−0.29	0.48	0.29	0.28	1.00
SE	0.14	−0.18	0.34	0.25	0.26	0.58	1.00
OP	−0.11	0.38	−0.23	−0.22	−0.25	−0.02 (NS)	−0.05 (NS)	1.00
PC	−0.02 (NS)	0.26	−0.12	−0.05 (NS)	−0.11	−0.01 (NS)	−0.05 (NS)	0.23	1.00
RT	−0.21	0.44	−0.34	−0.16	−0.28	−0.27	−0.29	0.25	0.27	1.00
Finland
S	1.00
C	−0.37	1.00
BRB	0.43	−0.46	1.00
CR	0.19	−0.19	0.28	1.00
TA	0.40	−0.55	0.51	0.34	1.00
CV	0.05 (NS)	−0.28	0.18	0.32	0.18	1.00
SE	0.01 (NS)	−0.14	0.16	0.15	0.09 (NS)	0.65	1.00
OP	−0.12	0.21	−0.16	−0.06 (NS)	−0.13	0.15 (NS)	0.35	1.00
PC	−0.08 (NS)	0.14	−0.20	0.01 (NS)	−0.11	−0.04 (NS)	−0.08 (NS)	0.03 (NS)	1.00
RT	−0.12	0.10	−0.07 (NS)	−0.06 (NS)	−0.06 (NS)	−0.20	−0.16	−0.17	0.23	1.00
Portugal
S	1.00
C	−0.27	1.00
BRB	0.43	−0.50	1.00
CR	0.09 (NS)	−0.11 (NS)	0.25 (NS)	1.00
TA	0.17	−0.29	0.46	0.22	1.00
CV	0.22	−0.28	0.47	0.46	0.34	1.00
SE	0.13	−0.11 (NS)	0.29	0.24	0.22	0.42	1.00
OP	−0.09 (NS)	0.34	−0.12 (NS)	−0.06 (NS)	−0.10 (NS)	−0.03 (NS)	−0.01 (NS)	1.00
PC	−0.08	0.22	−0.10 (NS)	−0.08 (NS)	−0.08 (NS)	−0.08 (NS)	−0.14	0.31	1.00
RT	−0.06 (NS)	0.27	−0.14	−0.08 (NS)	−0.16	−0.11	−0.25	0.23	0.29	1.00
Germany
S	1.00
C	−0.55	1.00
BRB	0.75	−0.82	1.00
CR	0.54	−0.58	0.73	1.00
TA	0.55	−0.55	0.69	0.76	1.00
CV	0.52	−0.45	0.66	0.67	0.50	1.00
SE	0.31	−0.28	0.47	0.40	0.34	0.71	1.00
OP	−0.26	0.66	−0.37	−0.22	−0.32	−0.02 (NS)	0.12 (NS)	1.00
PC	−0.04 (NS)	0.22	−0.12	−0.03 (NS)	−0.09 (NS)	−0.11 (NS)	−0.13	0.33	1.00
RT	−0.13	0.28	−0.23	−0.14	−0.14	−0.27	−0.29	0.36	0.48	1.00

Abbreviations. S: Safety; C: Complacency; BRB: benefit/risk balance; CR: collective responsibility; TA: trust in authorities; CV: commitment to vaccination; SE: self-efficacy; OP: openness to patients; PC: perceived constraints; RT: reluctant trust; NS: not significant.

^aAll item intercepts and factor loadings were set to be held equal across countries, and the metrics of the factors were defined by fixing their variances to one in one country while freely estimated in the others. All correlations are significant at P ≤ 0.05 except when (NS) stated.

Table 4. Associations between vaccination behaviors and I-Pro-VC-Be factors among HCPs: results from multiple modified Poisson regressions with robust standard errors^a (n = 2,748).

	Long-form	Short-form^b
	aRR [95% CI]
I-Pro-VC-Be factors
Self-reported near-systematic (>90%) vaccine recommendation or intent-to-recommend
Safety perception > mean (ref. No)	1.79 [1.47;2.17]	1.78 [1.47;2.14]
Complacency > mean (ref. No)	0.50 [0.42;0.60]	0.53 [0.45;0.62]
Benefit/risk balance > mean (ref. No)	2.46 [2.11;2.87]	2.74 [2.11;3.56]
Collective responsibility > mean (ref. No)	1.85 [1.61;2.13]	1.82 [1.54;2.15]
Commitment to vaccination > mean (ref. No)	2.03 [1.77;2.33]	2.48 [2.13;2.90]
Self-efficacy > mean (ref. No)	1.60 [1.44;1.77]	1.49 [1.36;1.63]
Trust in authorities > mean (ref. No)	1.71 [1.48;1.97]	1.80 [1.57;2.06]
Openness to patients > mean (ref. No)	0.90 [0.81;0.98]	0.93 [0.85;1.02]
Reluctant trust> mean (ref. No)	0.78 [0.71;0.86]	0.77 [0.70;0.85]
Perceived constraints > mean (ref. No)	0.89 [0.82;0.98]	1.00 [0.90;1.11]
Self-vaccination against influenza: 3 times over the past 3 years (score = 3/3)
Safety perception > mean (ref. No)	1.27 [1.20;1.35]	1.23 [1.16;1.30]
Complacency > mean (ref. No)	0.74 [0.69;0.79]	0.80 [0.76;0.84]
Benefit/risk balance > mean (ref. No)	1.32 [1.26;1.39]	1.23 [1.15;1.32]
Collective responsibility > mean (ref. No)	1.17 [1.12;1.22]	1.24 [1.18;1.31]
Commitment to vaccination > mean (ref. No)	1.17 [1.12;1.22]	1.21 [1.15;1.27]
Self-efficacy > mean (ref. No)	1.17 [1.12;1.21]	1.14 [1.09;1.18]
Trust in authorities > mean (ref. No)	1.16 [1.11;1.22]	1.17 [1.12;1.23]
Openness to patients > mean (ref. No)	0.92 [0.88;0.96]	0.94 [0.90;0.98]
Reluctant trust> mean (ref. No)	0.90 [0.86;0.94]	0.92 [0.88;0.96]
Perceived constraints > mean (ref. No)	0.98 [0.94;1.02]	1.01 [0.96;1.05]
Self-vaccination against COVID-19: fully vaccinated + booster (score = 4/4)
Safety perception > mean (ref. No)	1.09 [1.06;1.13]	1.08 [1.05;1.12]
Complacency > mean (ref. No)	0.91 [0.89;0.94]	0.94 [0.92;0.97]
Benefit/risk balance > mean (ref. No)	1.10 [1.07;1.13]	1.08 [1.05;1.12]
Collective responsibility > mean (ref. No)	1.04 [1.02;1.06]	1.07 [1.05;1.10]
Commitment to vaccination > mean (ref. No)	1.04 [1.02;1.06]	1.08 [1.05;1.10]
Self-efficacy > mean (ref. No)	1.02 [1.00;1.04]	1.01 [0.99;1.03]
Trust in authorities > mean (ref. No)	1.05 [1.03;1.08]	1.06 [1.03;1.08]
Openness to patients > mean (ref. No)	0.97 [0.95;0.99]	0.98 [0.97;1.00]
Reluctant trust> mean (ref. No)	0.96 [0.94;0.98]	0.95 [0.93;0.97]
Perceived constraints > mean (ref. No)	0.99 [0.97;1.00]	0.99 [0.97;1.01]

Abbreviations. I-Pro-VC-Be: International Professionals’ Vaccine Confidence and Behaviors; HCPs: healthcare professionals; aRR [95% CI]: adjusted relative risk and 95% confidence interval.

^aAll models were run separately and adjusted for country, gender, age, and profession. Explanatory variables (I-Pro-VC-Be factors) were dichotomized at the sample mean. Alpha risk = 0.05; statistically significant results in bold.

^bItems included in the short-form in Table 5.

Table 5. Final short-form I-Pro-VC-Be tool to measure determinants of vaccine confidence in HCPs^a,b.

Dimension	Item
Perceived safety of vaccines	1. Vaccines are safe.
Complacency	2. Today, some vaccines recommended by [insert relevant authority] are not useful, because the diseases they prevent are not serious.
Perceived benefit/risk balance	3. The benefits of vaccines outweigh their potential risks.
Perceived collective responsibility	4. I recommend the vaccines on the vaccination schedule to my patients because it’s essential to contribute to protection of the population (community immunity).
Commitment to vaccination	5. I am committed to ensuring that my patients are vaccinated.
Self-efficacy	6. I feel sufficiently trained on how to bring up the question of vaccines with hesitant patients.
Trust in authorities	7. I trust the [insert relevant authority] to ensure that vaccines are safe.
Openness to patients	8. I inform my patients about the benefits and risks of vaccines without trying to influence them.
Perceived constraints	9. The cost of some vaccines is a problem for some patients and can keep me from prescribing them.
Reluctant trust	10. I may sometimes recommend vaccines from the official schedule even if I feel the vaccination policy is not sufficiently clear.

Abbreviations. I-Pro-VC-Be: International Professionals’ Vaccine Confidence and Behaviors; HCPs: healthcare professionals.

^aThe following response scale applies to all items: 1: strongly disagree, 2: somewhat disagree, 3: undecided, 4: somewhat agree, 5: strongly agree.

^bThe final long-form I-Pro-VC-Be can be found at [45]. Two generalized items for perceived vaccine (‘Vaccines are safe’) and the perceived benefit/risk balance of vaccines (‘The benefits of vaccines outweigh their potential risks’) were recommended after this analysis was completed to offer an adaptable tool for various country and cultural contexts. In the present short-form criterion validity test, the corresponding items used were 'Vaccines against human papillomaviruses are safe' and 'The benefits of the vaccine against hepatitis B outweigh its potential risks'

Hu L, Bentler PM. Cutoff criteria for fit indexes in covariance structure analysis: Conventional criteria versus new alternatives. Struct Equ Modeling. 1999;6(1):1–55. doi: 10.1080/10705519909540118

 Web of Science ®Google Scholar

Satorra A, Bentler PM. A scaled difference chi-square test statistic for moment structure analysis. Psychometrika. 2001;66(4):507–514. doi: 10.1007/BF02296192

 Web of Science ®Google Scholar

Asparouhov T, Muthén B Computing the Strictly Positive Satorra-Bentler Chi-Square Test in Mplus. Mplus Web Notes: No 12 [Internet]. 2013; Available from: https://www.statmodel.com/examples/webnotes/SB5.pdf.

 Google Scholar

Karlsson LC, Garrison A, Gould G, et al. Pro-VC-Be international. OSF [Internet]. 2023; Available from: https://osf.io/vha92/.

 Google Scholar