HPV vaccine’s benefits extend beyond those already vaccinated

A new study has demonstrated that the effectiveness of the Human Papillomavirus (HPV) vaccine in young women has a much greater impact on the broader community than once thought. Researchers following several cohorts of young women over the last six years have not only noticed substantial reductions of the virus’ most lethal types within the vaccinated segment of their sample population, but have also witnessed a large decline in the level of infection among unvaccinated women as well. These findings are significant, given that HPV is one of the most common sexually transmitted infections in the world, and the highest risk factor for cervical cancer (CVC) among women.

The study was conducted by researchers at the Cincinnati Children’s Hospital, where two groups of sexually active young women, aged 13-26, were followed across two time periods. The first group was observed in 2006 largely before the vaccine became widely available. The second group was observed in 2009-10, with around 60% of those being vaccinated against HPV. All of them were tested periodically for 37 different strains of HPV.

There are over 100 types of HPV, most of which are either benign or cause genital and anal warts. About 90% of HPV infections resolve themselves within several months to a year regardless of age.[1]The more persistent and aggressive strains, such as Types 16 & 18, are strongly linked to CVC. These two strains are not as easily detected through conventional screening methods, where treatment could still be effective and minimally invasive.[2] There are two vaccines approved in Canada, both of which prevent these two strains; one of which also protects against two other strains directly responsible for genital warts.

The researchers’ observations over those four years showed that the prevalence of these four HPV strains dropped by 60%.[3] Among vaccinated women, there was a 70% drop in the rate of infection.[4] More remarkably, the unvaccinated group showed a 50% drop in infection rates, indicating that health officials’ hopes for ‘herd immunity’ were being realized.[5] The findings are quite surprising, given that these young women were sexually active prior to being vaccinated, and some had only received one shot out of the entire set, yet the study provided health officials with real-world insight into the impact of the vaccine, which can’t always be reproduced in the lab.

There are some questions about how easily these results can be generalized at the national level. Participants in this study were from one community in Cincinnati, all of whom were African American and from low-income families, yet were covered by U.S. Medicaid. In addition, HPV infection rates were still increasing overall[6], indicating that while the vaccine is effective, it has yet to incorporate additional, albeit less riskier HPV strains that cause the remaining 30% of CVC.

Nevertheless, this research demonstrates that the HPV vaccine is making headway into lower socio-economic communities, which are at much higher risk of developing the CVC, and it speaks to the importance of both administering the vaccine to women at a young age, while removing barriers to greater protection against the third most common form of cancer in women.

[1] Debbie Saslow, et al., “American Cancer Society, American Society for Colposcopy and Cervical Pathology, and American Society for Clinical Pathology screening guidelines for the prevention and early detection of cervical cancer,” CA: A Cancer Journal for Clinicians  62, no. 3 (2012): 166, accessed June 14, 2012,http://journals2.scholarsportal.info.proxy.library.carleton.ca/tmp/8837026343413225143.pdf

[2] 5. Muhieddine Seoud, Wiebren A.A. Tjalma and Veerle Ronsse, “Cervical Adenocarcinoma: Moving Towards Better Prevention,” Vaccine 29, no. 49 (2011): 9153, accessed June 15, 2012,http://journals2.scholarsportal.info.proxy.library.carleton.ca/tmp/18192141686225267042.pdf

[3] Jennifer Goodwin, “HPV Vaccine Reducing Infections, Even Among Unvaccinated,” Winnipeg Free Press (Winnipeg, MB), July 9, 2012. http://www.winnipegfreepress.com/arts-and-life/life/health/hpv-vaccine-reducing-infections-even-among-unvaccinated-study-161776435.html

[4] Ibid.

[5] Ibid.

[6] Goodwin, 1.

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