Nationwide positivity rates of high-risk human papillomavirus for the United States before and since the introduction of a Human Papillomavirus (HPV) vaccine in 2006 would provide insight into the population impact of HPV vaccination. Data for high-risk HPV testing results from January 1, 2004 to June 1, 2013 at a national reference laboratory were retrospectively analyzed to produce 757,761 patient records of women between the ages of 14 and 59.
Generalized linear models and finite mixture models were utilized to eliminate sources of bias and establish a population undergoing standard gynecological screening.
Unadjusted positivity rates for high-risk HPV were 27.2% for all age groups combined. Highest rates occurred in women aged 14 to 19. While the positivity rates decreased for all age groups from 2004 to 2013, the higher age categories showed less downward trend following vaccine introduction, and the two age categories 20 to 24 and 25 to 29 showed a significantly different downward trend between pre- and post-vaccine time periods (-0.1% per year to -1.5% per year, and 0.4 % per year to -1.5% per year, respectively). All other age groups had rates of change that became less negative, indicating a slower rate of decline.
In evaluating the surveillance tool, we find that it is important to consider many sources of heterogeneity, e.g., age, type of test, location, and type of testing center, and also consider quantitative methods of adjustment and distribution assessment to construct a useful surveillance tool. Further studies should expand on this methodology.
The results of the surveillance tool indicate a downward trend in vaccine-appropriate age groups consistent with uptake of the HPV vaccine. The pre-post rate changes were in direct contrast between the age-appropriate groups and the groups too old for the HPV vaccine, further indicating the surveillance tool may be detecting the impact of the HPV vaccine over time. After refinement, this surveillance tool should remain in place to observe the future impact of the HPV vaccine.