Geographical disparities in human papillomavirus herd protection.

Background: Human papillomavirus (HPV) vaccination has occurred unequally across the United States, potentially contributing to uneven vaccine-type HPV prevalence between regions. We examined whether emerging vaccine-related herd protection exhibits regional differences among unvaccinated girls and women.

Methods: We evaluated the prevalence of vaginal HPV among women 14-59 years of age from 2003 to 2014 using repeated cross-sectional data from the National Health and Nutrition Examination Survey (NHANES). Women who provided an adequate vaginal swab sample were included. Vaginal prevalence of vaccine-type HPV (types 6, 11, 16, 18) were examined in four regions of the United States between 2003 and 2014. We examined vaccine-type HPV prevalence in 2007-2014 in each US census region among younger participants (14-34 years old) stratified by vaccination status to determine whether one or both groups contributed to uneven HPV prevalence.

Results: A total of 12 175 participants 14-59 years of age met inclusion criteria. Vaccine-type HPV prevalence decreased in all regions. Vaccine-type HPV varied by region only among unvaccinated 14-34 year olds, with a higher prevalence in the Midwest (13.8%, 95% confidence interval (CI): 10.7-17.0) and South (12.5%, 95% CI: 10.2-14.8) compared to the Northeast (8.9%, 95% CI: 6.5-11.2). No regional variation in vaccine-type HPV prevalence was observed among vaccinated participants.

Conclusions: Higher prevalence of vaccine-type HPV among unvaccinated women in the South and Midwest may contribute to regional disparities in HPV-related cancer incidence, as emerging herd immunity may not be as strong in those regions.