Purpose: Clinical trials of vaccines against two common HPV types that cause cervical cancer (HPV-16, HPV-18) have shown promising efficacy at 5 years of follow-up against type-specific infection and precancerous lesions in girls not previously infected with these types; however, the long-term properties of the vaccine are uncertain.

Methods: We explored the influence of two uncertain vaccine properties (efficacy against types-16,18 and duration of protection) on lifetime cancer risk, using an empirically-calibrated simulation model. Likelihood-based methods were used to fit the model to age-related HPV prevalence, cancer incidence, and HPV type distribution among cancer cases using epidemiological data from a high-risk, unscreened region of Vietnam (Ho Chi Minh). Varying vaccine efficacy (70% to 100%) and duration of protection (10 years to lifelong), we assessed the cost-effectiveness of vaccinating pre-sexually active adolescent girls (assumed to occur between ages 9-11) at different levels of cost ($5 to 150 per vaccinated girl) and vaccine uptake (25% and 75%).

Results: Assuming 100% efficacy and lifelong protection, our model predicted approximately 50% reduction in lifetime risk of cancer with 75% vaccine uptake; with vaccine-induced immunity of only 10 years, benefits dropped to 37%, and with both 10-year protection and 70% efficacy, benefits dropped to 25%. At $5 per vaccinated girl (~per-dose cost of $1), adolescent vaccination was cost-saving compared to no vaccination, provided efficacy was >90% and lasted for at least 20 years; with all other combinations of efficacy and duration, vaccination was less than $100 per year of life saved (YLS) compared to no intervention. When the cost-per vaccinated girl was doubled to $10 (~per-dose cost of $2), adolescent vaccination was more than $100 per YLS when efficacy was <100% or duration was 10 years or shorter. When the cost-per vaccinated girl was $150 (~per dose cost of $40), vaccination exceeded the Vietnam per capita GDP ($3,100 per YLS), a commonly cited cost-effectiveness threshold for low-income countries, across the explored ranges of efficacy and duration.

Conclusions: Adolescent HPV 16,18 vaccination in a high-risk region of Vietnam would be considered an attractive public health investment provided vaccine cost is drastically reduced from that in the U.S., the duration of vaccine-induced immunity is more than 20 years, and high efficacy is achieved by vaccinating girls prior to sexual debut.