Different population-level vaccination effectiveness for HPV types 16, 18, 6 and 11

Background Given that the human papillomavirus (HPV) vaccine types have different durations of infectiousness and infectivity, the population-level vaccine effectiveness of these types may differ even if vaccine efficacy is identical. Objective To compare the type-specific effectiveness of vaccination against HPV types 16, 18, 6 and 11. Methods An individual-based stochastic model of HPV transmission (18 HPV-types) in a population stratified by age, gender and sexual activity was developed. Multiple parameter sets were identified by fitting the model to sexual behaviour data and age-and type-specific HPV prevalence. Results Under base case assumptions (70% coverage, 99% vaccine efficacy per act and 20 years' duration of protection), vaccinating 12-year-old girls is predicted to reduce HPV-16, HPV-18 and HPV-6/11 prevalence by 61% (80% uncertainty interval (UI) 53-77), 92% (80% UI 65-100) and 100% (80% UI 97-100), respectively, 50 years after the start of the vaccination programme. Differences in type-specific vaccine effectiveness increased over time, and decreased with improved vaccine efficacy characteristics. Conclusions For the same vaccine efficacy, the population-level impact of HPV vaccination will most likely be different, with HPV-16, the most oncogenic type, having the lowest effectiveness. These results should be taken into account when designing and interpreting post-vaccination surveillance studies.