Speaker: Dr. Christopher Kribs Zaleta
University of Texas
Arlington

Title: Vaccination and coinfection effects on HPV and cervical cancer

Abstract: The recent approval of a vaccine for the 4 strains of human papillomavirus (HPV) which account for most cases of cervical cancer has led to some controversy over vaccination policy due to the sexually transmitted nature of the infection. In addition, research suggests that patients infected with one strain of HPV may be more vulnerable to concurrent infection with a second strain (coinfection), and that cervical cancer is unlikely to go into remission in patients infected with multiple HPV types. We consider the effects of two kinds of vaccination policy (mandatory mass vaccination vs. voluntary vaccination) under the assumption that infection by one of the vaccine-targeted (carcinogenic) strains increases vulnerability to infection by a non-targeted strain. Analysis concentrates on the basic reproductive number for each strain as well as on its invasion reproductive number, a measure of the respective strain's ability to invade when the other strain is endemic. We show that under some circumstances, vaccination can actually eradicate the non-targeted strain. Numerical simulations suggest that while the presence of the non-targeted strain can increase HPV-related cancer deaths by more than 100 percent, it can also be reduced by more than 90 percent with 50 percent vaccination coverage.