THE COST-EFFECTIVENESS OF INTEGRATED CERVICAL CANCER PREVENTION STRATEGIES IN THE ONTARIO SETTING – CAN WE DO BETTER?

Purpose:  A universal, publicly funded, school-based human papillomavirus (HPV) vaccination program in girls was initiated in Ontario in 2007, prompting an economic assessment of prevention programs.

Method: A cost-utility analysis of cervical cancer prevention from the healthcare payer perspective was performed based on linked HPV transmission and disease history models. The heterosexual network model of HPV transmission predicted age-specific incidence of infection over time by HPV type. The disease history model predicted HPV infection-related health outcomes (cervical cancer, mortality). Data on sexual behavior, disease history, quality of life, screening test performance, and vaccine effectiveness were obtained from the literature. Information on vaccination coverage and screening uptake was obtained from surveys and administrative data. Direct medical costs attributable to HPV infection, cervical intraepithelial neoplasia and invasive cervical cancer were estimated using Ontario population-based linked health administrative datasets. Interventions:Combinations of 2 vaccination scenarios (conservative and optimistic, based on coverage, vaccine effectiveness and duration of protection), and 900 screening scenarios (screening start age: 21-70 years, screening interval: 3-20 years; 1-year time steps). Current schedule: screening start age 21 years, screening interval 3 years. Primary outcomes:expected lifetime cost, quality-adjusted life years (QALYs), incremental cost-effectiveness ratios and net benefit (NB) at λ=1xGDP/capita (~C$40,000/QALY). Analyses: (1) first vaccinated cohort (low herd-immunity), and (2) steady state, i.e. all cohorts were vaccinated (high herd-immunity). 

Result:  The NB of vaccination only was similar (conservative assumptions) or higher (optimistic assumptions) than screening only. Adding vaccination to the current screening schedule was highly cost-effective (<C$10,000/QALY). Delaying screening start and/or extending screening intervals reduced both expected QALYs and cost. Incidence of infection and disease is lower in steady state analysis and under optimistic vaccination scenarios, impacting optimal screening schedules. For first cohorts and steady state/conservative vaccination scenarios delaying screening start to 25 years increases NB; for the steady state/optimistic vaccination scenario delaying screening start to 30 years increases NB while maintaining 3 year screening intervals. However, given vaccination, differences in NB across screening scenarios are small and several screening scenarios increase NB. 

Conclusion: Delaying screening start age and/or extending screening intervals in vaccinated cohorts is likely to be cost-effective. Consideration should be given to short-term implications of long-term health policy decisions, particularly for infectious disease interventions that require long time intervals to reach steady state.