HEALTH AND ECONOMIC IMPACT OF HPV VACCINATION ON CERVICAL CANCER SCREENING IN SPAIN: IMPLICATIONS ON THE CURRENT SCREENING PRACTICES OF VACCINATED COHORTS

Purpose: In October 2007, HPV vaccination for 11- to 14-year-old girls was approved by Spain’s Interterritorial Council of the NHS, with planned implementation before the end of 2010. We assessed the health and economic outcomes associated with alternative cervical cancer prevention strategies to inform policy planning over the next 2 years
Methods: We conducted a cost-effectiveness analysis from a societal perspective, using a simulation model of HPV infection and cervical cancer. Likelihood-based methods were used to calibrate the model to epidemiologic data from Spain (e.g., age-specific prevalence of HPV and precancerous lesions, HPV type distribution in lesions, and cervical cancer incidence). Analyses were conducted with a random sample of a good-fitting parameter sets. We generated mean reductions in lifetime risk of cancer, life expectancy, and lifetime costs for the following strategies: 1) screening women over age 25, varying both frequency and initial screening test; 2) HPV vaccination of girls at recommended ages; and 3) combined screening and vaccination. Cost data were from Spain and expressed as 2005 US$. Alternative strategies were compared using incremental cost-effectiveness ratios. Parameter uncertainty was evaluated using one- and two-way sensitivity analysis, as well as probabilistic analysis.
Results: Current practice was less effective and less cost-effective than all strategies that combined vaccination followed by organized screening every 5 years. Assuming lifelong immunity, adolescent vaccination plus every-5-year cytology with HPV DNA triage beginning at age 30, reduced the lifetime cancer risk 60-85% depending on differential rates of vaccination and screening coverage. Screening using more sensitive HPV DNA testing allowed longer screening intervals (e.g., 6-8 years) without substantial loss of protection. Both strategies were cost-effective as defined by an incremental cost-effectiveness ratio less than the GDP per capita.  Results were sensitive to vaccine efficacy, duration of immunity, screening behavior after vaccination, and cost of vaccination.
Conclusions: Although Spain is a low-risk country for cervical cancer, there is an opportunistic screening program with uneven population coverage and high-frequency/low-quality cytology screening, making it ineffective and inefficient.  High coverage of adolescents with the HPV 16,18 vaccine, followed by an organized every 5- to 8-year screening program, beginning between ages 25 and 30, represents the best balance between costs and benefits. This strategy would be more effective and cost effective than the status quo.