Since 2007, 75 countries have implemented human papillomavirus (HPV) vaccination programmes. It is important to examine whether the promising results from pre-licensure randomised clinical trials and predictions from mathematical models are materialising in the real world. We summarised the most recent evidence about the population-level effects of girls-only HPV vaccination programmes among girls/young women targeted for vaccination, older women, and boys/men on anogenital warts (AGW) and high-grade cervical lesions(CIN2+).
We searched Medline and Embase (2007/01/01–2016/12/16) for studies presenting changes in HPV-related outcomes between pre- and post-vaccination periods. We stratified all analysis by age/sex and performed subgroup analyses to identify the main sources of heterogeneity. We used random-effect models to derive pooled relative risk estimates.
We identified 48 eligible studies from 11 high-income countries. We identified that the overall proportion of females vaccinated in the different countries (considering both vaccination coverage and number of cohorts vaccinated) was an important source of heterogeneity. Therefore, we categorised countries as having a medium/high proportion of females vaccinated (coverage ≥50% and multi-cohort vaccination) or a low proportion of females vaccinated (coverage <50% and/or single-cohort vaccination). In countries with a medium/high proportion of females vaccinated, there was a rapid and significant decline of AGW among girls/women <30 years old and boys/men <25 years old, and significant decreases in CIN2+ among girls <20 years old. Decreases in CIN2+ were also observed among women 20-24 years old after 5 years of vaccination. In countries with a low proportion of females vaccinated, significant decreases in AGW were observed after 3-4 years of vaccination among girls/women <25 years old, but there were no significant decreases among older women, and boys/men.
Ten years after the implementation of HPV vaccination, the promising results of randomised trials are materialising in the real world. We observed significant decreases in AGW and CIN2+ and strong herd effects, particularly in countries with a high proportion of females vaccinated. Additional surveillance data is required to examine the incremental effectiveness of gender-neutral vs girls-only vaccination programmes and the population-level impact of reduced dose schedules.