Factors related to vaccine uptake by young adult women in the catch-up phase of the National HPV Vaccination Program in Australia: Results from an observational study

Background: Australia commenced a publically-funded, National Human Papillomavirus (HPV) Vaccination Program in 2007 with a two year catch-up phase for females aged 12-26 years. Objective: To identify the factors associated with the uptake of the HPV vaccine (which has a recommended 3-dose schedule in Australia) by young adult women vaccinated by general practitioners and community-based programs within the catch-up phase. Methods: 1139 women who were eligible to receive the free HPV vaccine during the catch-up period were recruited in 2008-2009 (age 20-29 years at recruitment), in New South Wales, after having a normal (negative) cervical smear result recorded on the NSW Pap Test Register. Participants completed a self-administered questionnaire providing information on vaccination status, and sociodemographic and other factors. Results: Overall, 880 (77%) women reported receiving ≥1 dose of the vaccine and 777 women (68%) reported receiving ≥2 doses. In multivariable analysis (adjusting for the period for which each woman was eligible for free HPV vaccination), uptake of ≥1 dose of the vaccine was significantly associated with being born in Australia (p<. 0.01), being single (p= 0.02), being nulliparous (p<. 0.01), living in a higher socioeconomic status area (p-trend. = 0.03), living in more remote areas (p= 0.03), drinking alcohol (p<. 0.01) and using hormonal contraceptives (p<. 0.01). Although vaccinated women were more likely to have fewer sexual partners than unvaccinated women (p-trend. = 0.02), they were also more likely to report a prior sexually transmitted infection (STI) (p= 0.03). Similar factors were associated with receiving ≥2 doses. Conclusions: In this group, women living in higher socioeconomic status areas were more likely to be vaccinated against HPV in the catch-up phase of the national program. Although vaccinated women tended to have fewer sexual partners, they also reported prior STIs, which may be a marker of increased risk of prior exposure to HPV. The findings of this study reinforce the continuing need to prioritise equitable delivery of vaccination to various population subgroups.