Abstract & Commentary
Community (Herd) Immunity Follows HPV Vaccination
By Hal B. Jenson, MD, FAAP, Dean, Western Michigan University School of Medicine, Kalamazoo, MI, is Associate Editor for Infectious Disease Alert.
Dr. Jenson reports no financial relationships relevant to this field of study.
Source: Kahn JA, Brown DR, Ding L, et al: Vaccine-type human papillomavirus and evidence of herd protection after vaccine introduction. Pediatrics 2012;130:e249-e256.
Young women in two primary care clinics in Ohio who were from 13 to 26 years of age with a history of sexual contact were studied using a sequential sampling strategy in a pre-vaccination HPV surveillance study from 2006-2007 and in a postvaccination surveillance study from 2009-2010. Cervicovaginal swabs were genotyped for HPV using PCR amplification techniques. In the postvaccination study, participants were considered "vaccinated" if they had received at least one dose of the quadrivalent HPV vaccine.
There were 368 evaluable participants in the pre-vaccination surveillance study. Of the 409 evaluable participants in the postvaccination surveillance study, 242 (59.2%) had received at least one HPV vaccine dose, with a mean interval of 2.2 years since HPV vaccination.
The overall HPV prevalence rates among this cohort of sexually active young women increased during the 3-4 year interval of the study by 8.5%, from 68.3% to 76.8% (P = 0.0003). However, the prevalence of vaccine-type HPV among vaccinees decreased from 31.8% to 9.9% (P < 0.0001), and among non-vaccinees also decreased, from 30.2% to 15.4% (P < 0.0001). Subanalyses of only the high-risk vaccine-type HPV (HPV-16 and HPV-18) confirmed similar decreases.
The prevalence of high-risk nonvaccine-type HPV increased from 48.6% to 56.2% (P = 0.0038) for all participants. The increase in the rate of high-risk nonvaccine-type HPV was significant for vaccinated participants (P < 0.0001) but was not significant for unvaccinated participants.
Commentary
This study was performed in a cohort of young women with high rates of HPV infection, and with continuing exposure as evidenced by the overall increased rate of HPV infections over the study period. The study confirms the effectiveness of quadrivalent HPV vaccine to reduce vaccine-type HPV prevalence rates. This study may actually understate the impact of HPV vaccination because only one HPV vaccine dose was required to be considered "vaccinated."
A substantial reduction in vaccine-type HPV prevalence was seen not only among vaccinees, but also among unvaccinated persons. This demonstrates that quadrivalent HPV vaccination may provide significant community (herd) immunity even in a relatively limited timeframe of 4 years. Thus, HPV vaccination appears to reduce the prevalence of vaccine-type HPV among all young women in the community, which should translate to substantially decreased rates of cervical intraepithelial neoplasia (CIN) and cervical cancer. Although not included in this study, it is plausible that vaccine-type HPV prevalence rates among male sexual partners also decreased substantially in the community even though only young women were vaccinated.
Young women in two primary care clinics in Ohio who were from 13 to 26 years of age with a history of sexual contact were studied using a sequential sampling strategy in a pre-vaccination HPV surveillance study from 2006-2007 and in a postvaccination surveillance study from 2009-2010. Cervicovaginal swabs were genotyped for HPV using PCR amplification techniques.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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