Exploring reported causes of vaccine hesitancy among European adolescents and parents: results of a citizen science project

Background: Progress in pediatric immunization is threatened by vaccine hesitancy. While recent estimates show 14–35% of European parents exhibit some degree of hesitancy, little is known about adolescents. We assessed vaccine hesitancy and associated factors in European adolescents and parents through the online Science4Pandemics platform. Methods: We conducted two cross-sectional surveys. One in individuals aged ≥ 12 and < 18 years, using a non-validated questionnaire adapted from the Parent Attitudes about Childhood Vaccines (PACV); and another using the PACV questionnaire in parents aged ≥ 18 years, who were not necessarily related to the adolescents. Results: 1877 adolescents from Italy, Portugal, Poland and Spain were included. Of these, 45.9% were aged 12–14 years, and 54.1% were 15–17 years. The prevalence of hesitancy (adapted PACV score ≥ 50%) was 20.8% (390 individuals). Hesitancy prevalence varied between countries, from 12.5% in Spain to 31.6% in Poland (p < 0.001). Geographic region was the only associated factor for hesitancy [Odds Ratio (OR) for Polish adolescents: 3.20 (95%CI: 2.29, 4.51); OR for Italian adolescents: 2.28 (95%CI: 1.62, 3.24); OR for Portuguese adolescents: 1.13 (95%CI: 0.77, 1.66); all compared to Spanish adolescents]. Country remained the only associated factor in the multivariate logistic regression analysis. In contrast, 1135 parents of children under 18 were included, with hesitancy observed in 20.4% (232 individuals). The main associated factors for hesitancy, both in the univariate and multivariate analyses, were country of residence [OR for Italian parents: 2.34 (95%CI: 1.47, 3.80); OR for Polish parents: 2.69 (95%CI: 1.70, 4.36); OR for Portuguese parents: 2.26 (95%CI: 1.41, 3.68); all compared to Spanish parents], and age, with older parents being less hesitant (OR: 0.97, 95%CI: 0.96, 1.00). In both parents and adolescents, the main reasons for vaccine hesitancy were fear of vaccine side effects (56.1% in adolescents, 51.9% in parents) and lack of trust in government recommendations (21.9% in adolescents, 22.8% in parents). Conclusions: Vaccine hesitancy in adolescents and parents in Europe is prevalent, with country of residence as a key influencing factor. Targeted strategies to educate both groups about immunization benefits and its side effects are essential, considering the heterogeneity across countries and reasons for hesitancy.