An Instrument to Measure Psychosocial Determinants of Health Care Professionals' Vaccination Behavior: Validation of the Pro-VC-Be Questionnaire

"Identifying which HCPs are vaccine hesitant, quantifying the prevalence of vaccine hesitancy according to different socio-professional characteristics, understanding its nature and determinants, as well as its consequences on HCPs' behaviors for themselves and their patients, are essential public health and research aims."

Vaccine hesitancy among health care professionals (HCPs) is of particular concern for several reasons, including its potential to reduce their willingness to recommend vaccines to their patients. While instruments have been developed to measure vaccine hesitancy in the general population, in particular concerning vaccines for children, there had not yet been one designed with HCPs in mind. Thus, this group of researchers developed a new instrument, the Pro-VC-Be (Health Professionals Vaccine Confidence and Behaviors) questionnaire. This article presents its development, its theoretical basis, and the results of its construct and criterion validation studies.

Pro-VC-Be focuses on vaccine confidence rather than on its related concept of vaccine hesitancy because the researchers feel that, from an intervention perspective, this lens could facilitate dialogue with HCPs for whom vaccine hesitancy may be a sensitive issue and encourage vaccine confidence among them. Developed in French, the questionnaire can be completed online in 10 minutes, an acceptable time for most HCPs. However, in view of their time constraints, the researchers are in the process of validating a short version of the Pro-VC-Be.

The Pro-VC-Be is based on 3 theoretical frameworks or models:

1. The Theoretical Domain Framework, which is composed of a synthesis of theories of behaviour and behaviour change, clustered into 14 domains;
2. The Health Belief Model (HBM) - in particular, the postulate that the adoption of preventive behaviours depends on their perceived benefits and risks, considered in light of the disease's perceived severity; and
3. The 5C model for vaccine hesitancy, which includes confidence, complacency, constraints (perceived structural and psychological barriers to vaccination), calculation (engagement in extensive information searching), and collective responsibility (willingness to protect others).

The Pro-VC-Be contains categories of questions intended to:

• Probe vaccination behaviour - HCPs' vaccination behaviour has two principal elements: their recommendations (or lack thereof) to their patients and their self-vaccination behaviour (personal vaccine uptake). Specific questions are used to examine specific vaccine situations by focusing, for example, on vaccines with suboptimal uptake in some populations and contexts.
• Measure the core determinants of vaccine confidence and of vaccination behaviours identified in previous studies - Assessment here focuses on: perceived risks of vaccines; complacency; perceived benefit/risk balance; perceived collective responsibility; trust in authorities; and perceived constraints (e.g., difficulties in access to vaccines).
• Examine other psychosocial factors ("intermediary factors") that are expected to predict vaccine confidence and vaccination behaviour, or to moderate or mediate relations between vaccine confidence and vaccination behaviour - Assessment here focuses on: self-efficacy; commitment to the vaccination of their patients; professional and social norms; "reluctant trust" (i.e., the extent to which HCPs might trust the vaccination system despite the concerns they have about some vaccines or the system itself); and openness to patients' concerns.

The article details the stages of the instrument's development and validation, including cognitive validation, a pilot test with 144 HCPs, and a survey among 2,696 HCPs (general practitioners (GPs) in France and French-speaking parts of Belgium and nurses in Quebec, Canada) in October-November 2020. Exploratory and confirmatory factor analyses evaluated the Pro-VC-Be instrument's construct validity. The researchers used HCPs' self-reported vaccine recommendations to patients, general immunisation activity, self-vaccination, and future COVID-19 vaccine acceptance to test criterion validity. Among the survey's findings:

• GPs with an above-average vaccine confidence score (combining complacency, perceived vaccine risks, perceived benefit-risk balance, and perceived collective protection, as well as complacency) were significantly more likely to recommend vaccines to their patients very frequently than the other GPs - that is, the probability of very frequent recommendations was 40% higher for GPs with an above-average vaccine confidence score than for the others. GPs with higher vaccine confidence scores also reported more frequent general immunisation activity: raising the subject of vaccination with patients, recommending, and/or prescribing vaccines (P < 0.001), higher acceptance of future COVID-19 vaccines (P < 0.001), and, among French GPs, a higher score of self-vaccination for influenza and pertussis (P < 0.001). Nurses with an above-average vaccine confidence score were also significantly more likely (+70%, P < 0.001) to recommend vaccines to their patients very frequently, to report higher immunisation activity (+70%, P < 0.001), and to be more accepting of future COVID-19 vaccines (+ 100%, P < 0.001).
• Proactive efficacy (combining commitment to vaccination and self-efficacy) was the factor most strongly associated with high vaccine recommendation frequency and general immunisation activity among both GPs and nurses.
• An above-average score of trust in health authorities was significantly associated with a higher likelihood of recommending vaccines to patients (+30%) among both GPs (P < 0.001) and nurses (P = 0.003).
• Openness to patients was associated with a higher likelihood of very frequent immunisation activity among nurses (+30%, P = 0.03) and with a lower likelihood of strong acceptance of COVID-19 vaccines (-20%, P < 0.001) among GPs overall and of a high self-vaccination score among French GPs (-10%, P = 0.01).
• Among GPs, an above-average score of reluctant trust was significantly associated with lower likelihoods of very frequent vaccine recommendation (-30%, P < 0.001), very frequent immunisation activity (-20%, P < 0.001), strong COVID-19 vaccine acceptance (-10%, P = 0.003), and self-vaccination (-10%, P = 0.02).
• Nurses perceiving high constraints to vaccination were less likely to report acceptance of potential COVID-19 vaccines (-10%, P = 0.01).

Thus, the final results indicated a 6-factor structure with good fit: vaccine confidence, trust in authorities, proactive efficacy, reluctant trust, openness to patients, and perceived constraints. The instrument also showed good convergent validity, adequate discriminant validity, and good criterion validity.

The researchers are extending validation of the Pro-VC-Be to other countries - e.g., as part of an H2020 European project ("Jitsuvax"). They suggest that use of this tool in cultural and development contexts different from those of Western countries should be based on prior qualitative research with HCPs to verify whether the Pro-VC-Be factors can be adapted to reflect the reality of these countries.