Human papillomavirus (HPV) is the most common pathogenic sexually transmitted infection known to humanity. It is a necessary cause of cervical cancer, and is also linked to many other cancers as well as genital warts. In high-income countries, the incidence of cervical cancer has been dramatically reduced (but not eliminated) over the last few decades by organised cervical screening. As of 2008, the global burden of cervical cancer was estimated at 529,000 new cases and 274,000 deaths, with most cases occurring in developing countries.
Several vaccines have been developed that protect against the HPV types that cause the majority of cervical cancers worldwide. The vaccines have been shown to give high and long-lasting efficacy when administered prior to HPV infection. However, the vaccines are expensive to purchase and deliver. Furthermore, it will be many decades before they show a substantial impact on cervical cancer, because they are preventing infections happening now that will lead to cancer many years later. Hence understanding the impact and cost-effectiveness of HPV vaccination is vital to inform evidence-based decision-making about vaccine introduction, particularly in resource-challenged settings.
Several models have been developed to understand the epidemiological and economic impact of HPV vaccines. Many of these models are dynamic, and they help to explain both the direct and herd effects of the vaccines. However, for situations such as mass vaccination of girls prior to sexual debut and hence HPV infection, static models have been shown to provide reasonable conservative approximations of vaccine impact and cost-effectiveness.