Quantifying the impact of dissimilar HPV vaccination uptake among Manitoban school girls by ethnicity using a transmission dynamic model

Abstract

BACKGROUND: Gardasil, a human papillomavirus (HPV) vaccine, began among grade 6 girls in Manitoba, Canada in 2008. In Manitoba, there is evidence that First Nations, Metis, and Inuit women (FNMI) have higher HPV prevalence, lower invasive cervical cancer (ICC) screening, and higher ICC incidence than all other Manitoban (AOM) women. We developed a mathematical model to assess the plausible impact of unequal vaccination coverage among school girls on future cervical cancer incidence. METHODS: We fit model estimated HPV prevalence and ICC incidence to corresponding empirical estimates. We used the fitted model to evaluate the impact of varying levels of vaccination uptake by FNMI status on future ICC incidence, assuming cervical screening uptake among FNMI and AOM women remained unchanged. RESULTS: Depending on vaccination coverage, estimated ICC incidence by 2059 ranged from 15% to 68% lower than if there were no vaccination. The level of cross-ethnic sexual mixing influenced the impact that vaccination rates among FNMI has on ICC incidence among AOM, and vice versa. The same level of AOM vaccination could result in ICC incidence that differs by up to 10%, depending on the level of FNMI vaccination. Similarly, the same level of FNMI vaccination could result in ICC incidence that differs by almost 40%, depending on the level of AOM vaccination. CONCLUSIONS: If we are unable to equalize vaccination uptake among all school girls, policy makers should prepare for higher levels of cervical cancer than would occur under equal vaccination uptake