A Systematic Review of Interventions to Promote HPV Vaccination Globally

"Improving on the design and evaluation of HPV vaccination interventions is particularly critical at this moment as many adolescents missed vaccinations during the COVID-19 pandemic and vaccine hesitancy is growing."

The World Health Organization (WHO) has a vision to eliminate human papillomavirus (HPV)-related cancers, particularly cervical cancer, worldwide by 2030. Yet only an estimated 15% of girls are fully vaccinated against HPV globally, as of 2023. HPV vaccination interventions have targeted various socio-ecological levels that influence HPV vaccination to ultimately effect change. Multi-level and multi-component interventions are increasingly used. This systematic review synthesises literature published from May 2015 to March 2020 related to promoting HPV vaccine uptake and/or completion internationally.

The search identified 1,201 studies after removing duplicates; in the end, 79 articles were included in the review for data extraction. Of these, 57 (72.2%) were conducted in the United States (US). Other studies were conducted in Europe (n = 10, 12.7%), Africa (n = 4, 5.1%), Asia (3, 3.80%), Australia (3, 3.80%), Central/South America (1, 1.27%), and Canada (1, 1.27%). Forty-five studies (57.0%) employed an experimental design, 18 (22.8%) used a quasi-experimental design, and 16 (20.3%) employed a non-experimental design.

Most studies were conducted at the individual level (44, 55.7%), followed by interpersonal level (10, 12.7%), community level (3, 3.8%), and clinic level (4, 5.0%). Although most interventions were directed at a single level, 23.7% (n= 18) were multi-level. Twenty-seven interventions (33.8%) reported using theory in intervention development, including the Elaboration Likelihood Model, Culture-centric narrative theory, Health Belief Model, Theory of Reasoned Action/Planned Behavior, Moral Norm, and Social Cognitive Theory.

Intervention components varied, but the most common intervention components were: individual education of parents and/or adolescents (60, 76.0%); use of technology such as websites, PowerPoints, and text messages (21, 26.6%); and provider education (16, 20.3%). Facilitators to intervention implementation were the use of patient navigators and user-friendly resources, while barriers included costs, time to implement, and difficulties of integrating interventions into the organisational workflow.

Of those reporting HPV vaccine outcomes, post-intervention vaccine initiation ranged from 5% to 99.2%, while series completion ranged from 6.8% to 93.0%. There were few patterns to be discerned in which types of interventions were found to be most effective, and, in fact, among those that did report, only 20.3% reported significant increases in either initiation or completion or both.

The review suggests 6 insights::

1. While the success of behavioural provider and clinic-focused interventions (particularly ones that promote changes to systems like utilising reminder-recall and encouraging strong recommendations) is well documented, this review found that other types of interventions were more often used. For example, information-providing interventions (used to increase knowledge of HPV, HPV-associated cancers, and the HPV vaccine) were most common (31.7%) followed by patient decision support interventions (29.1%). Yet, educational or information-giving interventions have been found to be less effective in increasing uptake or completion. The interventions being implemented are not the types that have been shown to be most effective, which is consistent with other research that has identified a discrepancy between the implementation of interventions or strategies that are most effective compared to interventions that may be deemed "easiest" to implement.
2. Despite extensive research showing the increased effectiveness of multi-level interventions, yet 75% of the interventions in this review reported intervening on only a single level, most commonly in clinical or school-based settings focused on individuals or providers. Future interventions to promote HPV vaccination should prioritise intervening at multiple levels to more effectively improve vaccine outcomes and discern which combination of levels results in higher vaccination.
3. Using theory is well documented as a best practice in intervention development and implementation; however, only one-third of the interventions in this review used theory in the design of their programme strategies. Using theory allows for understanding why specific interventions may be effective (or not effective) and for comparison across multiple studies. Thus, future HPV vaccine interventions should report more broadly on the use of theory in their intervention development and how constructs are employed in their design of intervention components or assessed in evaluation.
4. The effectiveness of these interventions was difficult to discern due to heterogeneity in measurement, outcomes, and study designs. However, there are promising findings that a proportion of the interventions that reported significant changes in vaccination uptake or completion are multi-level and multi-component. Future intervention studies should focus on using rigorous methods to assess the effectiveness of different types of interventions.
5. Less than 20% of studies reported on facilitators, and less than 30% reported on barriers. Yet this kind of information is critical in understanding programme implementation, adaptation, and tailoring for different settings.
6. HPV vaccination rates fell during the COVID-19 pandemic, and competing priorities led to less time for clinics to devote to vaccine promotion. Coupled with data suggesting that concerns about HPV vaccine safety are rising, these trends are indicative of a need to identify what works and how to implement it to prevent future generations from being susceptible to HPV-associated cancers.

Full list of authors, with institutional affiliations: Cam Escoffery, Emory University; Courtney Petagna, Emory University; Christine Agnone, Emory University; Stephen Perez, Emory University; Lindsay B. Saber, Emory University; Grace Ryan, University of Massachusetts Chan Medical School; Meena Dhir, Emory University; Swathi Sekar, Emory University; Katherine A. Yeager, Emory University; Caitlin B. Biddell, University of North Carolina at Chapel Hill; Purnima Madhivanan, University of Arizona; Stephanie Lee, Emory University; Amanda S. English, University of North Texas Health Science Center; Lara Savas, University of Texas Health Science Center at Houston; Eliza Daly, University of Iowa; Thuy Vu, University of Washington; and Maria E. Fernandez, University of Texas Health Science Center at Houston