An instrument to measure psychosocial determinants of health care professionals’ vaccination behavior: Validation of the Pro-VC-Be questionnaire

Figures & data

Table 1. Set of items used in the pro-VC-Be questionnaire

VARIABLES
OUTCOMES
VACCINATION BEHAVIORS	General vaccination behavior	B1. With the patients you treat:
		a. How often do you bring up the subject of vaccination?
		b. How often do you recommend the vaccines that are indicated for them?
		c. How often do you prescribe indicated vaccines to them?
	Vaccine recommendation frequency	B3. How often do you recommend the following vaccines?
		A. Catch-up MMR for adolescents
		B. Pertussis vaccine in pregnancy (Quebec)/pertussis vaccine in mothers who have just given birth, if not vaccinated before pregnancy (France)
		C. Meningitis C vaccine at 12 months of age
		D. Human papilloma virus vaccine in young girls and boys aged 11 to 14 years old
		E. Catch-up hepatitis B vaccine in adolescents
		F. Seasonal flu vaccine in adults under 65 years old with chronic illness
	Stated willingness to accept future COVID-19 vaccines	I. If a Covid-19 vaccine were available (Oct-Nov 2020):
		1. Would you agree to recommend it to your patients?
		2. Would you agree to vaccinate yourself?
	Self-vaccination behavior	VP1. Were you vaccinated against seasonal influenza for the winter 2019–2020 season?
		VP11. For this coming winter (2020–2021), do you intend to be vaccinated against seasonal influenza? (France and Belgium only)
		VP2. Have you had a pertussis vaccination booster dose during your adult life in the past 20 years? (France only)
EXPLANATORY VARIABLES
CORE DETERMINANTS OF VACCINE CONFIDENCE AND OF VACCINATION BEHAVIORS	Perceived risks of vaccines	R1. Some vaccines can cause autoimmune diseases
		R2 The measles vaccine can cause autism in children
		R3 Some vaccines can cause multiple sclerosis
		R4 A vaccine developed in an emergency situation [for example, during an epidemic like that of COVID-19) does not offer a sufficient guarantee of safety
	Complacency	U1 Today, some vaccines recommended by authorities are not useful, because the diseases they prevent are not serious
		U2 Children are vaccinated against too many diseases
		U3 Children are vaccinated at too young an age
		U4 It is preferable to acquire immunity against infectious diseases naturally (by having the disease) than by vaccination
	Perceived benefit/risk balance of vaccines	BRB1 The benefits of the vaccine against measles are much greater than its potential risks
		BRB2 The benefits of the vaccine against influenza in people with a chronic disease are much greater than its potential risks
		BRB3 The benefits of the vaccine against hepatitis B in infants (or as catch-up in adolescents) are much greater than its potential risks
		BRB4 The benefits of the vaccine against human papillomaviruses are much greater than its potential risks
	Perceived collective responsibility	CR1 I recommend the vaccines on the vaccination schedule to my patients because it’s essential to contribute to protection of the population (community immunity)
		CR2 I recommend the vaccines in the official schedule to my hesitant patients, explaining to them the importance of community immunity
	Trust in authorities to inform about vaccines	C1 I trust the ministry of health to provide reliable information about the risks and benefits of vaccines
		C2 I trust the bodies that develop these guidelines (French national authority for health)
		C3 I trust science to develop safe effective new vaccines
		C4 I trust the ministry of health to establish the vaccination strategy
		C5 I trust the ministry of health to ensure that vaccines are safe
		C6 I am convinced that the ministry of health is not influenced by the pharmaceutical industry
	Perceived constraints to vaccinating patients	PC1 The cost of some vaccines is a problem for some patients and can keep me from prescribing them
		PC2 The lack of availability of certain vaccines is often a problem that can keep me from prescribing them to my patients.
		PC3 Not having vaccines in my office is a problem in my practice
		PC4 The legal and professional responsibilities associated with immunization practices are excessive
VARIABLES
INTERMEDIARY FACTORS BEHIND HCPS VACCINE CONFIDENCE AND VACCINATION BEHAVIORS	Openness to patients’ concerns regarding vaccination	OP1 Patients who are hesitant about the benefits and risks of vaccines have legitimate questions
		OP2 I inform my patients about the benefits and risks of vaccines but I let them make their decision without trying to influence them
		OP3 It is counterproductive to try to convince vaccine-hesitant patients to be vaccinated
		OP4 I think that patients have a duty to be vaccinated
		OP5 I am willing to let parents delay immunizing their children
	Professional norm	SN It is my professional responsibility to ensure that all of my patients without contraindications are vaccinated
	Commitment to the vaccination of their patients	CV1 I am actively involved in ensuring that my patients are vaccinated
		CV2 I do my best to motivate patients who are hesitant to get vaccinated
		CV3 I am committed to keeping my knowledge about vaccination up-to-date (CME, conferences, reading)
		CV4 I am committed to developing the skills needed to communicate better with my patients about vaccination
	Self-efficacy in addressing hesitancy	SE1 I feel comfortable advising my patients about the risks and benefits of vaccines
		SE2 I feel comfortable discussing vaccines with my patients who are highly hesitant about vaccination
		SE3 I feel sufficiently trained and informed to discuss vaccines with all patients
		SE4 I feel sufficiently trained on how to approach the question of vaccines with hesitant patients
	Reluctant trust	RT1 I recommend the vaccines in the official schedule even though I sometimes feel that I am not sufficiently informed about some of them
		RT2 I recommend the vaccines in the official schedule even though I feel that the objectives of the vaccination policy are not clear enough
		RT3 I recommend vaccines on the official schedule although I sometimes have doubts about their safety

Table 2. Factor loadings of the final set of items used in the exploratory factor analysis^a on the test sample (n = 1,348)

		Factors extracted
		1	2	3	4	5	6	7	8	9	10
Perceived risks of vaccines	R1. Some vaccines can cause autoimmune diseases	0.72*	0.01	0.02	−0.05*	0.03	−0.02	−0.01	0.03	−0.03	−0.01
	R2 The measles vaccine can cause autism in children	0.47*	0.17*	−0.05	−0.05	0.03	0.04	−0.06	−0.02	−0.04	0.06
	R3 Some vaccines can cause multiple sclerosis	0.82*	0.00	−0.03	0.02	−0.03	0.02	0.00	0.00	0.01	0.01
Complacency	U1 Today, some vaccines recommended by authorities are not useful, because the diseases they prevent are not serious	0.04	0.57*	−0.02	−0.10*	0.01	0.01	−0.04	0.02	−0.08	−0.04
	U2 Children are vaccinated against too many diseases	0.03	0.84*	0.01	0.02	−0.05*	0.00	0.03	0.02	−0.03	−0.01
	U3 Children are vaccinated at too young an age	0.01	0.70*	−0.07*	−0.01	0.03	0.03	−0.04	−0.02	0.00	0.07*
Perceived benefit/risk balance	BRB1 The benefits of the vaccine against measles are much greater than its potential risks	−0.06*	−0.02	0.79*	−0.05*	−0.02	0.00	0.03	−0.01	0.05	−0.02
	BRB2 The benefits of the vaccine against influenza in people with a chronic disease are much greater than its potential risks	−0.01	0.02	0.61*	0.05	0.04	−0.03	−0.03	0.01	0.07	−0.14*
	BRB3 The benefits of the vaccine against hepatitis B in infants (or as catch-up in adolescents) are much greater than its potential risks	−0.02	−0.09*	0.70*	0.02	0.04	−0.02	0.00	−0.03	0.02	0.04
	BRB4 The benefits of the vaccine against human papillomaviruses are much greater than its potential risks	0.00	−0.03	0.72*	0.08*	0.04	−0.01	0.03	0.00	0.00	0.04
Perceived collective responsibility	CR1 I recommend the vaccines on the vaccination schedule to my patients because it’s essential to contribute to protection of the population (community immunity)	0.00	−0.02	0.02	−0.01	−0.04	0.01	0.01	−0.02	0.93*	0.01
	CR2 I recommend the vaccines in the official schedule to my hesitant patients, explaining to them the importance of community immunity	−0.01	0.01	−0.02	0.06	0.10	−0.04	0.02	0.06	0.65*	−0.02
Trust in authorities	C1 I trust the ministry of health to provide reliable information about the risks and benefits of vaccines	−0.05	−0.01	0.05	0.78*	−0.02	−0.05*	0.00	−0.03	0.05	−0.01
	C4 I trust the ministry of health to establish the vaccination strategy	−0.01	−0.02	−0.02	0.83*	0.00	−0.05*	0.02	−0.02	0.01	0.01
	C5 I trust the ministry of health to ensure that vaccines are safe	−0.01	−0.02	0.02	0.87*	0.04	0.04*	0.00	0.00	0.02	−0.01
Perceived constraints	PC1 The cost of some vaccines is a problem for some patients and can keep me from prescribing them	0.01	0.00	0.01	0.06	−0.04	−0.04	−0.03	0.55*	−0.05	0.08
	PC2 The lack of availability of certain vaccines is often a problem that can keep me from prescribing them to my patients.	0.01	0.04	0.00	−0.09*	0.01	0.01	0.01	0.69*	0.01	−0.02
	PC3 Not having vaccines in my office is a problem in my practice	−0.01	−0.06	−0.04	0.04	0.05	0.08*	0.03	0.49*	0.04	−0.08
Openness to patients	OP1 Patients who are hesitant about the benefits and risks of vaccines have legitimate questions	0.07	−0.01	0.01	−0.01	0.02	0.01	0.06	−0.05	0.01	0.47*
	OP2 I inform my patients about the benefits and risks of vaccines but I let them make their decision without trying to influence them	0.05	−0.06	−0.03	0.12*	−0.07	0.06	0.05	0.04	0.03	0.49*
	OP5 I am willing to let parents delay immunizing their children	−0.07*	0.12*	−0.02	−0.11*	0.13*	−0.04	−0.10*	−0.02	0.00	0.49*
Commitment to vaccination	CV1 I am actively involved in ensuring that my patients are vaccinated	0.00	−0.06	0.02	0.02	0.14*	0.04	0.62*	−0.05	0.09*	−0.12*
	CV3 I am committed to keeping my knowledge about vaccination up-to-date (CME, conferences, reading)	−0.01	0.03	−0.03	−0.04	0.07	−0.05*	0.77*	−0.02	0.02	−0.03
	CV4 I am committed to developing the skills needed to communicate better with my patients about vaccination	−0.06*	−0.02	0.07*	0.06*	−0.02	0.01	0.71*	0.05*	0.03	0.12*
Self-efficacy	SE1 I feel comfortable advising my patients about the risks and benefits of vaccines	0.00	−0.07*	0.00	0.02	0.74*	−0.03	0.10*	−0.04	0.05*	0.01
	SE2 I feel comfortable discussing vaccines with my patients who are highly hesitant about vaccination	0.00	−0.04	0.02	0.06*	0.79*	0.02	0.04	0.00	0.03	0.00
	SE3 I feel sufficiently trained and informed to discuss vaccines with all patients	−0.08*	−0.02	0.01	−0.03	0.78*	−0.08*	0.10*	0.01	0.00	0.00
	SE4 I feel sufficiently trained on how to approach the question of vaccines with hesitant patients	−0.02	0.03	0.04	0.01	0.84*	0.01	0.05*	−0.03	0.03	−0.01
Reluctant trust	RT1 I recommend the vaccines in the official schedule even though I sometimes feel that I am not sufficiently informed about some of them	0.04	−0.05*	0.05	0.03	−0.11*	0.71*	−0.07*	0.06*	−0.01	0.01
	RT2 I recommend the vaccines in the official schedule even though I feel that the objectives of the vaccination policy are not clear enough	−0.03	0.05*	−0.07*	−0.01	0.09*	0.75*	−0.05	0.02	0.04	−0.04
	RT3 I recommend vaccines on the official schedule although I sometimes have doubts about their safety	0.06	0.05	0.01	−0.08*	−0.03	0.64*	0.14*	−0.05	−0.07	0.09*

^aFactors estimated using maximum likelihood with robust standard errors, and CF-VARIMAX oblique rotation. Likert scales were treated as continuous variables. *P ≤ 0.05

Figure 1. Confirmatory factor analysis^a on the validation sample: loadings of items on factors (n = 1,348).

^a Factors were allowed to correlate. All factor loadings were set to be free, and the metrics of the factors were defined by fixing their variances to one. * P ≤ 0.05 ** P ≤ 0.01 *** P ≤ 0.001 Abbreviations. resp. = responsibility. RMSEA = root mean square error of approximation; CFI = comparative fit index; TLI = Tucker-Lewis index; SRMR = standardized root mean square residual

Figure 2. Second-order confirmatory factor analysis^a on the validation sample: standardized loadings on first- and second-order factors (n = 1,348).

^a Factors were allowed to correlate. All factor loadings were set to be free, and the metrics of the factors were defined by fixing their variances to one.         * P ≤ 0.05 ** P ≤ 0.01 *** P ≤ 0.001 Abbreviations. resp. = responsibility. RMSEA = root mean square error of approximation; CFI = comparative fit index; TLI = Tucker-Lewis index; SRMR = standardized root mean square residual

Table 3. Analysis of the correlations^a between the factors of the confirmatory factor analysis on the validation sample (n = 1,348)

	R	U	BRB	CR	TA	PC	OP	CV	SE	RT
R	1.00	0.52	−0.51	−0.40	−0.29	0.13	0.14	−0.36	−0.42	0.26
U		1.00	−0.43	−0.44	−0.37	0.13	0.10 (NS)	−0.28	−0.30	0.27
BRB			1.00	0.48	0.31	−0.14	−0.09 (NS)	0.35	0.35	−0.20
CR				1.00	0.42	−0.13	−0.08 (NS)	0.42	0.40	−0.18
TA					1.00	−0.18	0.10 (NS)	0.18	0.23	−0.24
PC						1.00	−0.04 (NS)	−0.10	−0.16	0.22
OP							1.00	−0.02 (NS)	−0.04 (NS)	0.18
CV								1.00	0.78	−0.11
SE									1.00	−0.21
RT										1.00

Abbreviations: R = Perceived risks of vaccines; U = Complacency; BRB = Perceived benefit/risk balance; CR = Perceived collective responsibility; TA = Trust in authorities; PC = Perceived constraints; OP = openness to patients; CV = Commitment to vaccination; SE = Self-efficacy; RT = Reluctant trust

^aAll correlations significant at P < 0.05 except when NS stated. Colored cells indicate moderate to high correlations. The darker the cell, the higher the absolute correlation between the corresponding items

Table 4. Associations between self-reported vaccine recommendation frequency, general immunization activity, and the Pro-VC-Be factors among HCPs: results from multiple robust Poisson regressions (n = 2,696)

	Very frequent vaccine recommendations (score >75%, ref. No)				Very frequent immunization activity (score >75%, ref. No)
	GPs (n = 1,641)		Nurses (n = 1,055)		GPs (n = 1,641)		Nurses (n = 1,055)
Pro-VC-Be factors	Separately^a	Global	Separately^a	Global	Separately^a	Global	Separately^a	Global
	aRR [95% CI]
Vaccine confidence > mean (ref. No)	1.4 [1.2;1.6]	1.2 [1.03;1.4]	1.7 [1.4;2.1]	1.5 [1.2;1.8]	1.3 [1.2;1.5]	1.2 [1.1;1.4]	1.7 [1.3;2.2]	1.2 [0.9;1.5]
Proactive efficacy > mean (ref. No)	1.6 [1.4;1.8]	1.4 [1.3;1.6]	2.8 [2.3;3.5]	2.7 [2.1;3.3]	1.4 [1.2;1.6]	1.3 [1.1;1.4]	4.2 [3.0;5.9]	3.8 [2.7;5.4]
Trust in authorities > mean (ref. No)	1.3 [1.1;1.5]	1.1 [1.0;1.3]	1.3 [1.1;1.6]	1.0 [0.8;1.2]	1.0 [0.9;1.2]	0.9 [0.8;1.0]	1.7 [1.3;2.2]	1.2 [0.9;1.6]
Openness to patients > mean (ref. No)	1.0 [0.9;1.1]	1.0 [0.9;1.2]	1.2 [1.0;1.4]	1.0 [0.9;1.2]	1.0 [0.9;1.1]	1.0 [0.9;1.1]	1.3 [1.03;1.7]	1.1 [0.9;1.4]
Reluctant trust > mean (ref. No)	0.7 [0.7;0.8]	0.9 [0.8;0.98]	1.0 [0.8;1.2]	1.2 [1.0;1.4]	0.8 [0.7;0.9]	0.9 [0.8;1.0]	0.7 [0.6;0.95]	0.9 [0.7;1.1]
Perceived constraints > mean (ref. No)	0.9 [0.8;1.1]	1.0 [0.9;1.1]	1.0 [0.8;1.2]	1.0 [0.9;1.2]	0.9 [0.8;1.1]	1.0 [0.9;1.1]	0.8 [0.7;1.1]	1.0 [0.8;1.2]

Abbreviations. Pro-VC-Be = Health Professionals Vaccine Confidence and Behaviors; GPs = general practitioners; aRR [95% CI] = adjusted relative risk and its 95% confidence interval.

^aSeparately: Pro-VC-Be factors introduced separately as explanatory variables in models adjusted for gender and age; global: all Pro-VC-Be factors introduced in the same model.

Table 5. Associations between acceptance of potential COVID-19 vaccines (in October-November 2020) and Pro-VC-Be factors: results from multiple robust Poisson regressions (n = 2,696)

	Strong acceptance of COVID-19 vaccines (score >4/6, ref. No)
Pro-VC-Be factors	GPs (n = 1,641)		Nurses (n = 1,055)
	Separately^a	Global	Separately^a	Global
	aRR [95% CI]
Vaccine confidence > mean (ref. No)	1.6 [1.3;1.9]	1.4 [1.1;1.6]	2.0 [1.7;2.3]	1.6 [1.3;1.9]
Proactive efficacy > mean (ref. No)	1.3 [1.1;1.5]	1.1 [0.9;1.3]	1.3 [1.2;1.5]	1.1 [1.0;1.3]
Trust in authorities > mean (ref. No)	2.0 [1.6;2.4]	1.8 [1.5;2.2]	1.9 [1.7;2.2]	1.6 [1.3;1.8]
Openness to patients > mean (ref. No)	0.8 [0.7;0.9]	0.9 [0.7;1.0]	1.0 [0.8;1.1]	0.9 [0.8;1.1]
Reluctant trust > mean (ref. No)	0.9 [0.7;0.99]	1.1 [0.9;1.2]	0.9 [0.7;0.96]	1.0 [0.9;1.2]
Perceived constraints > mean (ref. No)	0.9 [0.8;1.1]	1.0 [0.9;1.2]	0.9 [0.8;0.97]	0.9 [0.8;1.1]

Abbreviations. Pro-VC-Be = Health Professionals Vaccine Confidence and Behaviors; GPs = general practitioners; aRR [95% CI] = adjusted relative risk and its 95% confidence interval.

^aSeparately: Pro-VC-Be factors introduced separately as explanatory variables in models adjusted for gender and age; global: all Pro-VC-Be factors introduced in the same model.

Table 6. Associations between self-vaccination behaviors reported by French GPs and Pro-VC-Be factors^a: results from multiple robust Poisson regressions (n = 1,209)

	Up to date with influenza and pertussis vaccinations (score = 3/3, ref. No)
Pro-VC-Be factors	Separately^b	Global
	aRR [95% CI]
Vaccine confidence > mean (ref. No)	1.3 [1.1;1.4]	1.2 [1.02;1.3]
Proactive efficacy > mean (ref. No)	1.1 [1.02;1.3]	1.1 [0.9;1.2]
Trust in authorities > mean (ref. No)	1.2 [1.1;1.4]	1.1 [1.0;1.3]
Openness to patients > mean (ref. No)	0.9 [0.8;0.95]	0.9 [0.8;1.0]
Reluctant trust > mean (ref. No)	0.9 [0.8;0.97]	1.0 [0.9;1.1]

Abbreviations. Pro-VC-Be = Health Professionals Vaccine Confidence and Behaviors; GPs = general practitioners; aRR [95% CI] = adjusted relative risk and its 95% confidence interval.

^aSelf-vaccination behaviors were collected in French GPs only. We did not consider perceived constraints in the models because these constraints concerned HCPs’ vaccination practices for patients only.

^bSeparately: Pro-VC-Be factors introduced separately as explanatory variables in models adjusted for gender and age; global: all Pro-VC-Be factors introduced in the same model.