Estimation of the potential overall impact of human papillomavirus vaccination on cervical cancer cases and deaths
Abstract
Background: Human papillomavirus (HPV) vaccination offers potential for primary prevention of HPV-related pre-cancers and cancers as demonstrated in clinical trials. Mathematical models have estimated the potential real-life impact of vaccination on the burden of cervical cancer (CC).
However, these are restricted to evaluations in a limited number of countries. Methods: Potential decline in CC cases and deaths with the AS04-adjuvanted HPV-16/18 vaccine of young girls naive to HPV, was estimated at steady-state (vaccine coverage: 0-100%) based on clinical trial and country-specific incidence data.
Data on vaccine efficacy were taken from the end of study PATRICIA trial of the AS04-adjuvanted HPV-16/18 vaccine. The numbers of cases and deaths due to HPV-16/18 were estimated and compared with those due to any HPV type to estimate the additional cases prevented.
This difference estimates CC cases and deaths avoided due to protection against non-vaccine HPV types. Cost-offsets due to reductions in CC treatment were estimated for five countries (Brazil, Canada, Italy, Malaysia and South African Republic) using country-specific unit cost data.
Additionally, cervical intraepithelial neoplasia grade 2 or 3 (CIN2/3)-related burden (cases and treatment costs) prevented by vaccination were estimated for two countries (Italy and Malaysia). Results: HPV vaccination could prevent a substantial number of CC cases and deaths in countries worldwide, with associated cost-offsets due to reduced CC treatment.
Cross-protection increased the estimated potential number of CC cases and deaths prevented by 34 and 18% in Africa and Oceania, respectively. Moreover, vaccination could result in a substantial reduction in the number of CIN2/3 lesions and associated costs.
Conclusion: HPV vaccination could reduce the burden of CC and precancerous lesions in countries worldwide, part of disease burden reduction being related to protection against non HPV-16/18 related types.