Identifying and Addressing Gaps in the Australian School-Based HPV Vaccination Program

Abstract

Human papillomavirus (HPV) is one of Australia’s most common sexually transmissible infections and the primary cause of most cases of cervical cancer. HPV also causes other cancers, including penile, anal and oropharyngeal, and around 90% of all cases of genital warts. HPV-related cancers and genital warts are associated with a considerable health and economic burden. Australia became the first country in the world to implement a national school-based HPV vaccination program. Relatively high HPV vaccination coverage has been achieved in Australia, reaching just over 80% overall in 2017, yet this is still 10% lower than global recommendations by 2030, and considerably lower than targets of 95% for childhood immunisations. In Australia, analyses of HPV vaccination data to date have showed lower coverage in areas with lower socioeconomic status and in some geographical areas, but no studies have investigated variation in coverage across schools, which is where HPV vaccines are delivered. Adolescents should have equal access to the HPV vaccine course, irrespective of which school they attend. My thesis aimed to quantify the variation in HPV vaccination initiation across schools in three jurisdictions, and to understand school characteristics associated with lower coverage, particularly in schools where HPV initiation coverage was lower than for the dtpa vaccine (dtpa vaccine is co-administered and co-consented with HPV vaccine, so lower coverage for HPV would indicate HPV vaccine-specific hesitancy). My thesis also aimed to explore strategies to address the gaps identified. I undertook four interlinked studies using mixed quantitative and qualitative methods. The first study, a population-based ecological analysis of school-level data, identified that 23% of schools in the three jurisdictions in 2016/ 2017 school year had HPV initiation coverage at least 5% lower than for dTpa vaccine. This outcome was associated with schools with a higher proportion of adolescents from areas with higher socioeconomic advantage and from English-speaking backgrounds, and with smaller schools. The second study focused on using a school-level attributable risk measurement (taking the strength of the association and prevalence of school factors into account). This study found small schools, special education schools, schools with lower attendance and schools with higher enrolments of Aboriginal and Torres Strait Islander (Indigenous) students were most strongly associated with lower vaccination initiation coverage (<75%). Although special education schools had a lower school-level attributable risk measurement (as there was a small number of such schools), they had a much higher odds ratio than other school-level factors. My third study, a systematic review and meta-analysis, investigated the effectiveness of vaccine decision aids in decreasing decisional conflict regarding immunisations and increasing vaccination uptake with an inclusion period up to July 2019. The review found that decision aids slightly increased vaccination uptake and moderately increased intention to vaccinate, as well as a reduction in decisional conflict. However, there were no studies on HPV vaccination decision aids that met the inclusion criteria for the systematic review. The fourth study was an evaluation of a pilot intervention to determine the impact, acceptability and sustainability of an enhanced HPV vaccination catch-up program for Indigenous students who were missing at least one dose, which took place in term 3 and 4 in 2019. The study involved analysis of vaccination data, calculation of costs of the program and in-depth interviews conducted in term 1 2020, with immunisation providers delivering vaccinations in low HPV vaccination coverage schools. The evaluation demonstrated that the pilot intervention was considered beneficial with additional doses administered to Indigenous adolescents at a moderate extra cost; however, the process of following up with parents was very time consuming. Despite follow-up, some students did not attend the scheduled vaccine clinics, suggesting the need for additional strategies (e.g., out-of-school programs, more flexible vaccination clinics) to reach them. My research has identified the need for qualitative research to understand the reasons for low vaccination coverage in specific school settings, and the reasons for potential HPV vaccine-specific hesitancy. There is also a need to develop HPV vaccination-specific decision aids and evaluate their impact. Finally, future interventions should consider targeting students outside the school-based program. Overall, my thesis has highlighted the importance of collecting and analysing school-level data. It provides important insights that are needed to address the current gaps in the HPV vaccination program and to achieve equity in HPV vaccination coverage.