HPVoice: a single-blind three-arm RCT on social media communication strategies among adolescents in Tuscany, Italy

Cervical cancer is the first cancer potentially eliminable through widespread HPV vaccination. In Italy, despite free access, vaccine coverage among adolescents remains low. Psychological factors such as information avoidance (IA), the tendency to ignore threatening information, can influence vaccine decisions and contribute to vaccine hesitancy (VH). While social media offers new avenues for health communication, their effectiveness in reducing VH is uncertain. This study investigates the impact of Instagram-based communication strategies on adolescents' HPV knowledge and VH.

A three-arm randomized controlled trial was conducted in 22 high school classes in Tuscany, involving 526 students. Classes were randomized to follow one of three Instagram pages for one month: a neutral control, an information-based account, or a bias-aware account designed to address cognitive biases related to vaccination decisions. Data were collected through online surveys at three time points: baseline (T1), after the intervention (T2), followed by in-class lesson, and at three-month follow-up (T3). HPV knowledge and VH were assessed at all time points, whereas cognitive biases, including IA, were measured only at T1.

The final analysis included 301 students (mean age 15.2, 74% female). Overall, no significant changes in VH or knowledge were found between T1 and T2 overall. However, in students with low IA the info-based page reduced VH significantly compared to the control (-6.9%, p = .009). In contrast, among high-IA students, the same intervention increased VH (estimated: +8.9%, p = .002). Willingness to seek information increased in the info group among low-IA students (logg odds β = +1.639 vs. control, p = .034). At T3, we measured significant increase in knowledge compared to T1 despite the smaller sample collected.

Social media campaigns showed limited effects on VH reduction in adolescents and can even backfire among high-IA individuals. Future strategies should incorporate personalized, bias-aware and interactive tools to address VH and HPV vaccine uptake effectively.