Methods: Parameters unique to developing countries that may influence the impact of prophylactic HPV vaccines (e.g., single vaccination campaigns, parity, genital hygiene practices) were identified and explored. Published deterministic and stochastic models for HPV transmission were expanded to include a prophylactic vaccine. Based on published data for Malian women, estimates of susceptibility and risk of HPV infection were calculated for genital hygiene practices and age-specific parity rates. Other factors that may increase susceptibility to HPV infection and cervical cancer were also identified for future studies. Age-specific parity was estimated to affect 90% of women in a developing country during peak childbearing period and was modeled by amplification in risk of acquiring HPV up to a 10-fold increase. Vaccine was modeled to be continuously available in developed countries for women ages 11 to 26 years old, while vaccine was offered in a one-time vaccination campaign in developing country models. Change in prevalence as a function of vaccination coverage,increased susceptibility and number of lives saved were calculated for each model scenario.

Results: For 75% vaccination coverage, the developed country models showed reduction of prevalence to near zero. Although, similar vaccination coverage in the developing country models showed significant reduction, HPV prevalence did not approach zero. Varying levels of increased risk from parity rate showed proportionate increases in prevalence and related cervical cancer deaths.

Conclusions: In resource poor settings where health care dollars are at a premium, the number of women captured by a single vaccination effort is directly proportional to the reduction in HPV prevalence and cervical cancer associated deaths. This is in contrast to developed country settings where only minimal benefits are gained beyond 25% vaccination coverage using a continuous vaccination strategy. Increased parity consistently increased prevalence rates, the general dynamics remain the same. In settings in which parity rates are much higher than those in developed countries, a single vaccination strategy will reduce infections and deaths in these settings in similar proportions. Future studies of other cultural and economic factors may provide additional insight into optimal vaccination strategies for developing countries where cervical cancer remains a leading cause of mortality among women.