A validated modification of the vaccine hesitancy scale for childhood, influenza and HPV vaccines

Introduction: Vaccine hesitancy contributes to outbreaks of preventable disease worldwide. The Vaccine Hesitancy Scale (VHS), developed by the international WHO SAGE Working Group, has been validated previously for measuring hesitancy towards childhood vaccines; some psychometric properties were suboptimal.

Methods: We collected data using large, nationally-representative samples of parents in the U.S. We adapted the VHS items, and additional hesitancy items, to assess hesitancy towards influenza and HPV vaccines in addition to routine childhood vaccines. We then used exploratory and confirmatory factor analysis to identify latent constructs and create modified scales for childhood (VHS-child), influenza (VHS-flu) and HPV (VHS-HPV) vaccines with improved psychometric properties. Finally, we compared hesitancy scores on the VHS-child, VHS-flu, and VHS-HPV, to self-reported receipt of each vaccine category, and compared subscale scores to assess whether drivers of hesitancy differed by vaccine category.

Results: 2052 parents of children <18 years old completed the VHS-child and VHS-flu while 2020 parents of adolescents completed the VHS-HPV. A two-factor structure of 'risks' and a 'lack of confidence' was found for each vaccine category. Slight modifications to the VHS improved psychometric properties. Hesitancy was strongly associated with vaccine receipt: e.g., 76% of parents not hesitant towards influenza vaccine had vaccinated their child the past season, versus 9% of hesitant parents (p < 0.0001). Subscale scores also differed significantly between vaccines: lack of confidence was greater towards influenza (Median (IQR): 2.0 (1.2, 3.3)) and HPV (2.0 (1.3, 3.0)) vaccines than childhood (1.2 (1.0, 1.8), p < 0.0001 for both) vaccines; perceived risks of HPV vaccines (2.7 (1.7, 3.7)) were greater than for childhood vaccines (2.0 (1.3, 3.0), p < 0.0001).

Conclusions: Our modified VHS scales perform well psychometrically and allow for consistent measurement of the extent and reasons for hesitancy between vaccine categories. We suggest that future work use these scales to examine hesitancy towards other vaccines and to monitor hesitancy over time.