Declines in HPV vaccine type prevalence in women screened for cervical cancer in the United States: Evidence of direct and herd effects of vaccination

Background Human papillomavirus (HPV) vaccine has been recommended in the United States since 2006 for routine vaccination of girls at age 11–12 years and through age 26 years for women not previously vaccinated. Changes in vaccine-type HPV (VT) prevalence can be used to evaluate vaccine impact, including herd effects. Methods We determined type-specific HPV in cytology specimens from women aged 20–29 years screened for cervical cancer at Kaiser Permanente Northwest in 2007 and in two vaccine era periods: 2012–2013 and 2015–2016. Detection and typing used L1 consensus PCR with hybridization for 37 types, including quadrivalent vaccine types (HPV 6/11/16/18). Results Among 20–24 year-olds in 2012–2013 and 2015–2016, 44% and 64% had a history of ≥1-dose vaccination. VT prevalence decreased from 13.1% in 2007 to 2.9% in 2015–2016 (prevalence ratio [PR] = 0.22; 95% confidence interval [CI] 0.17–0.29). HPV 31 prevalence was also lower in the vaccine periods compared with 2007. VT prevalence in 2015–2016 among 20–24 year-olds was lower in both vaccinated, 1.3% (PR = 0.10; 95% CI 0.06–0.16), and unvaccinated women, 5.8% (PR = 0.45; 95% CI 0.33–0.61). Among 25–29 year-olds, 21% and 32% had a history of ≥1-dose vaccination. VT prevalence decreased from 8.1% in 2007 to 5.0% in 2015–2016 (PR = 0.62; 95% CI 0.50–0.78). Non-VT high risk prevalence was higher in the vaccine periods compared with the pre-vaccine era in both age groups, however, not in 2015–2016 compared with 2012–2013. Conclusion Within 9–10 years of vaccine introduction, VT prevalence decreased 78% among 20–24 year-olds and 38% in 25–29 year-olds. There were declines in both vaccinated and unvaccinated women, showing evidence of direct and herd protection.