During an 8-year span after vaccination introduction in a community setting, vaccine-type human papillomavirus (HPV) in young women decreased >90% in vaccinated women and >30% in unvaccinated women, indicating herd protection.  These findings were reported in a study published in Clinical Infectious Diseases.1

A total of 1180 young women (ages 13 to 26) were enrolled in a surveillance study. The study occurred in 3 waves: 2006 to 2007 (n=371), 2009 to 2010 (n=409), and 2013 to 2014 (n=400).  None of the participants were vaccinated during wave 1, and 59.2% (242) and 71.3% (286) were vaccinated during waves 2 and 3, respectively.

Participants were sexually experienced with >80% reported having at least 2 lifetime male sexual partners. The only HPV vaccine administered was the quadrivalent (HPV-6, -11, -16, and -18) before enrollment and was assessed by review of electronic medical records.


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Jessica A. Kahn, MD, MPH, professor of pediatrics in the Division of Adolescent and Transition Medicine at Cincinnati Children’s Hospital Medical Center within the University of Cincinnati College of Medicine in Cincinnati, Ohio, and colleagues noted that “the adjusted proportion of all women infected with ≥1 vaccine-type HPV decreased from 34.8% to 8.7% over the 3 waves, for an absolute decrease of 26.1% and an overall decline of 75.0%. The absolute decrease and overall decline were 31.7% and 90.8%, respectively, among vaccinated and 10.5% and 32.3% among unvaccinated women.”  The trend was similar for high-risk vaccine-type HPV (HPV-16 and/or HPV-18): decline of 74.6% in all women, 90.2% in vaccinated women, and 32.2% in unvaccinated women.

The results showed that the decrease in vaccine-type HPV was due to vaccine introduction rather than confounding factors.  In addition, while the decline in vaccine-type HPV prevalence in unvaccinated young women provided evidence of herd protection, the data highlighted the importance of getting the HPV vaccination as the optimal mode of prevention strategy.

While inability to generalize, selection bias, and unmeasured differences in participant characteristics were listed as limitations of the study, “the results of this and other studies suggest that vaccination programs could have a substantial population-level impact on rates of HPV-related cancers,” the researchers concluded.

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Reference

  1. Kahn JA, Widdice LE, Ding L, et al. Substantial decline in vaccine-type human papillomavirus (HPV) among vaccinated young women during the first 8 years after HPV vaccine introduction in a communityClin Infect Dis. 2016; Sept 20. doi: 10.1093/cid/ciw533. [Epub ahead of print]