An Investigation Into Aotearoa New Zealand's Approaches to Adolescent Vaccination Against the Human Papillomavirus

Background

The Human Papillomavirus (HPV) is a public health threat in Aotearoa New Zealand (NZ), as it is associated with a range of life-threatening cancers. To reduce HPV transmission, a vaccine was introduced into NZ’s National Immunisation Schedule in 2008 for girls aged 12 to 13, before the age of sexual maturity. This vaccine was primarily delivered to year 8 girls via a school-based vaccination programme, except in Canterbury, where HPV vaccines were delivered through primary health care providers (PCPs). In 2016 Canterbury adopted a mixed-model programme, utilising both schools and PCPs to administer HPV vaccines. In 2017 males were introduced into all HPV vaccination programmes.

Aims

1. Compare HPV vaccination coverage in Canterbury to the rest of NZ, to evaluate the success of differing vaccination programmes. 2. Investigate whether there are ethnic inequities in HPV vaccination coverage in NZ, and if any such inequities differ by vaccination programme. 3. Determine how the COVID-19 pandemic has impacted HPV vaccination coverage in NZ.

Methods

A repeated cross-sectional analysis was conducted using vaccination data from the Aotearoa Immunisation Register and population data from the Health Service User dataset, from 2013 to 2023. One-dose HPV vaccination coverage calculated amongst adolescents born 13 years earlier was stratified by ethnicity, gender, and location. Line graphs compared coverage between European, Pacific, and Māori adolescents in Canterbury and non-Canterbury. Beta regressions analysed how coverage changed before and after 2016, the year Canterbury introduced a mixed-model programme, and how coverage changed before and after the COVID-19 pandemic. All analysis was conducted in RStudio version 4.3.0.

Results

1. From 2013 to 2018, female HPV vaccination coverage was lower in Canterbury than non-Canterbury. From 2019 to 2023 coverage was alike between the two locations. Beta regressions confirmed that Canterbury female coverage significantly increased from 2016 to 2019. Male coverage from 2017 to 2023 was similar between Canterbury and non-Canterbury.
2. Until 2020, female coverage in Canterbury was consistent across the European, Māori, and Pacific populations, whereas male Māori and Pacific coverage was lower than European coverage. In non-Canterbury, female vaccination coverage was consistently higher among the Māori and Pacific populations until 2020. The male non-Canterbury Māori coverage rates appeared equal to European coverage, and Pacific coverage was higher than European. Overall, trends varied by ethnicity between Canterbury and non-Canterbury.
3. The COVID-19 pandemic caused HPV vaccination coverage to decrease from 2020 to 2022, although most populations appeared to recover by 2023. Amongst the total male and female populations coverage decreased more in Canterbury than in non-Canterbury. Coverage also predominantly decreased more amongst Māori and Pacific populations than European.

Conclusion

This study postulated that incorporating some form of school-based delivery for HPV vaccines throughout NZ was the most effective strategy to increase coverage. These findings were consistent with those seen in international literature. Further improvements could be made to NZ’s HPV vaccine delivery, not only to reduce differences in coverage by ethnicity and by vaccination programme but also to allow coverage in NZ to increase to levels seen in other

countries.