Evaluating a Behavioral Insights-Informed Social Media Campaign to Increase HPV Vaccination During Routine...

Background: Cervical cancer remains a leading cause of cancer-related deaths among women in Nigeria. In 2023, the Government of Nigeria, with support from Gavi and partners, introduced the single-dose human papillomavirus (HPV) vaccine through a phased, school-based campaign. The first phase was launched in October 2023 across 16 states, followed by a second phase in May 2024 that expanded coverage to the remaining states and the Federal Capital Territory. This study evaluates the additional impact of a behavioral insights-informed digital intervention, comprising a social media campaign amplified by trained pharmacists serving as local influencers, implemented in 2025 to increase acceptance and uptake of HPV vaccination during routine immunization. Methods: A pre-test/post-test quasi-experimental design with a control group was implemented in three Nigerian states in 2025 to assess the additional impact of a behavioral insights-informed social media campaign designed to strengthen social approval for HPV vaccination, increase awareness of vaccination locations, and reinforce caregivers' recognition of their adolescent daughters' desire to be vaccinated. Messages were amplified by trained pharmacists who served as local influencers. Caregivers of adolescent girls aged 9-17 years were recruited online through targeted Facebook and Instagram advertisements during Nigeria's transition from school-based HPV vaccination campaigns to routine immunization. Caregivers in treatment areas were exposed to geofenced social media advertisements on Facebook and Instagram and pharmacist counseling, while those in control areas were not. Logistic regression models using a difference-in-difference approach estimated the campaign's effect on HPV vaccination, controlling for caregiver and adolescent characteristics. Additional statistical models assessed the campaign's impact on caregivers' motivation and ability-key drivers of behavior according to the Fogg Behavior Model. Results: HPV vaccination increased at a significantly higher rate in the treatment compared to the control area. The adjusted odds of an adolescent girl being vaccinated were 1.48 times higher in the treatment area at follow-up (95% CI: 1.14-1.92). Adjusted marginal effects indicated that exposure to the campaign increased the probability of vaccination by 8.9 percentage points relative to the control group. The rate at which caregivers' motivation (aOR = 1.31, 95% CI: 1.00-1.70) and ability (knowing where to get vaccinated: aOR = 1.38, 95% CI: 1.07-1.79; ease of vaccination: aOR = 1.59, 95% CI: 1.22-2.06) increased was also higher in the treatment area. There was no relative increase in intervention versus control groups in factual knowledge regarding HPV vaccination. Conclusions: A behavioral insights-informed social media campaign in which pharmacists served as influencers was associated with higher HPV vaccine uptake during routine immunization. The higher rate of vaccination observed in intervention areas was associated with higher rates of caregiver motivation and ability but not with higher rates of caregiver knowledge. These findings are consistent with the potential of behavioral insights-informed digital campaigns to complement routine immunization efforts and improve vaccine uptake in low- and middle-income countries.