Modeling the potential impact of HPV vaccination on Hong Kong's cervical cancer burden

Abstract

Background. Cervical cancer is a common female cancer in Hong Kong. Cervical screening has been used in detecting cervical lesions for several decades. Given that human papillomavirus (HPV) infection is the etiological cause of cervical cancer, highly efficacious HPV vaccines are recently developed for preventing against HPV infection. Hong Kong has a well-developed healthcare system but relatively high cervical cancer incidence compared to other developed countries partly due to its suboptimal cervical screening program. This highlights the significance to evaluate the potential of implementing organized HPV vaccination programs for further reducing cervical cancer burden on top of cervical screening in Hong Kong.

Methods. Cross-sectional, population-based surveys were conducted to assess the acceptability of female adolescent HPV vaccination among girls from secondary schools in 2008 and among mothers of adolescent daughters in 2008 and 2012. Mathematical model with transmission dynamic and stochastic individual-based components was constructed to model the natural history of HPV infection and cervical cancer and thus to project the public health and economic impacts of organized female adolescent HPV vaccination programs in a societal perspective. The model used Markov Chain Monte Carlo algorithm to estimate natural history parameters of HPV infection and probabilistic sensitivity analysis to consider the uncertainty of costs and health utilities in the economic evaluation of organized HPV vaccination.

Results. Reported vaccine uptake among11–18 year-old girls increased from 2.4% among schoolgirls in 2008 to 9.1% among daughters of interviewed mothers in 2012. Among interviewed mothers, 27.5% and 37.6% of them were willing to have their daughters vaccinated at market price in 2008 and 2012, respectively. The mathematical model projected that HPV prevalence decreased soon after mass HPV vaccination and vaccine-induced cervical cancer reduction became obvious after vaccination programs have been launched for 30 years. If HPV vaccinesprovided30-year protection, the median incremental cost-effectiveness ratio (ICER) of routine HPV vaccination programs for 12 year-old girls at 25–75% vaccination coverage was US$26,367–32,527 per quality-adjusted life-year (QALY). The median ICER was above US$48,000/QALY if adding 2-year catch-up program for13–18 year-old girls and above US$58,000/QALY if vaccines protect against HPV infection for only 15 years. Conclusions. This study presented the first evaluation of organized HPV vaccination programs in Hong Kong. If vaccine protection lasted for 30 years or longer, organized routine HPV vaccination for 12 year-old girls would potentially be a cost-effective add-on in substantially reducing cervical cancers and HPV-related diseases on top of cervical screening in Hong Kong at an ICER threshold of US$33,218/QALY. However, the current estimated vaccine uptake was unexpectedly low and vaccine acceptability was only moderate. The findings indicated the importance to devise efficient strategies in achieving high and universal coverage for maximizing the population-level benefits of HPV vaccination. Policymakers should consider integrating the organized HPV vaccination programs with existing infrastructures to promote higher acceptability, to translate willingness to vaccinate to actual uptake, to assess population effectiveness, and to monitor safety issue and potential replacement effect of non-vaccine targeted HPV types following mass vaccination.