Maximising benefits and minimising harms with cervical cancer prevention in Australia: understanding cervical screening participation inequities and impacts on adverse pregnancy outcomes

Abstract

With the introduction of adolescent human papillomavirus (HPV) vaccination and change to 5-yearly HPV screening, Australia could eliminate cervical cancer by 2035 (<4 cases per 100,000 women annually). Equitable short- and medium-term elimination is dependent on high cervical screening coverage in all eligible subpopulations. I found reduced screening participation in all immigrant groups of women who gave birth in NSW between 2000-2017, especially Asian, Oceanic and New Zealand-born women. Low participation in these groups was also seen in women aged ≥45 years, and this persisted for ≥20 years post-immigration. With pregnancy being an opportune time to offer screening, a self-collected HPV test may be a more acceptable option for the underscreened in the future.

There is established evidence of reductions in oncogenic HPV infections and cervical precancer in HPV vaccinated cohorts. Australia, being an early adopter of adolescent HPV vaccination, is an ideal country to examine possible benefits beyond cervical cancer prevention. HPV-related cervical precancer and treatment have been associated with an increased risk of subsequent preterm birth (PTB). I examined PTBs in women with previous HPV-related precancer, accounting for multiple potential confounders. Women with a previous high-grade cervical histology had an increased risk of a future PTB (adjusted odds ratio:1.45, 95% confidence interval:1.39-1.52).

In an ecological study of Australian infants born 2000-2015, I found maternal cohorts with 60%–80% HPV vaccination coverage had a 3% reduction in PTBs. In a modelled analysis, I estimated the impact of HPV vaccination and cervical screening: age-standardised precancer treatment rates per 1000 women were predicted to decrease by 82%, resulting in 26,800 fewer PTBs between 2010-2070.

Considering the substantial morbidity and mortality from PTBs worldwide, this thesis provides evidence that HPV vaccination could provide important benefits beyond cancer prevention.