Process evaluation of a school-based vaccination intervention to improve HPV vaccine coverage: A mixed-method study embedded in the French PrevHPV cluster randomized controlled trial.

BACKGROUND

Human papillomavirus vaccine coverage (HPV VC) remains suboptimal in many countries. French authorities launched the PrevHPV research program, which included a cluster randomized controlled trial (cRCT) to evaluate the effectiveness of an 'at-school vaccination' intervention. Within this trial, we conducted a process evaluation of this intervention, specifically analyzing (i) its implementation, (ii) its mechanisms of impact, and (iii) the contextual factors influencing implementation (facilitators/barriers).

METHOD: We conducted a mixed-method study embedded in the PrevHPV cRCT (April 2021-April 2022). 'At-school vaccination' consisted of vaccination day(s) on school premises where mobile vaccination teams (MVTs) initiated HPV vaccination free of charge for eligible adolescents (i.e., non-vaccinated adolescents aged 11+). Quantitative data were collected through activity reports and self-administered questionnaires of adolescents and school staff. Qualitative data collected through six focus groups with school staff and MVTs were analyzed using thematic analysis.

RESULTS

Of the 31 schools (14,772 adolescents) randomized to implement 'at-school vaccination', 12 (39 %) dropped out. Among the participating schools, analysis of implementation showed that 17 % of adolescents returned valid consent forms, of whom 89 % initiated vaccination. MVTs played a central role in implementing vaccination day(s), supported by several school staff (e.g., school nurses, education assistants). Regarding mechanisms of impacts, satisfaction with the vaccination days was high among adolescents and school staff. The intervention generated both positive and negative group effects among adolescents. Contextual factors that facilitated implementation included the preparation of a list of adolescents to be vaccinated and the availability and motivation of school staff. The main barriers related to the management of consent forms and missing health records.

CONCLUSION

We formulated recommendations for implementing at-school vaccination, which may be particularly helpful for the French school HPV vaccination campaigns that were scaled up nationally in 2023. We also discussed potential macro-level improvement strategies, involving modifications to the legislative framework.

TRIAL REGISTRATION: Clinicaltrials.gov, NCT04945655. Registered 30 June 2021, https://clinicaltrials.gov/study/NCT04945655.