Vaccine-Type Human Papillomavirus and Evidence of Herd Protection After Vaccine Introduction

Abstract

WHAT'S KNOWN ON THIS SUBJECT:Clinical trials have demonstrated that prophylactic human papillomavirus (HPV) vaccines are highly effective in preventing HPV infection, but the impact of vaccination on HPV prevalence rates in real-world, community settings is uncertain. WHAT THIS STUDY ADDS:This study provides evidence of a substantial decrease in the prevalence of vaccine-type HPV among young women and evidence of herd protection in a community only 4 years after the quadrivalent HPV vaccine was licensed.abstract OBJECTIVES: The aims of this study were to compare prevalence rates of human papillomavirus (HPV) in young women before and after HPV vaccine introduction to determine the following: (1) whether vaccine-type HPV infection decreased, (2) whether there was evidence of herd protection, and (3) whether there was evidence for typereplacement (increased prevalence of nonvaccine-type HPV). METHODS:Young women 13 to 26 years of age who had had sexual contact were recruited from 2 primary care clinics in 2006-2007 for a prevaccination surveillance study (N = 368, none were vaccinated) and 2009-2010 for a postvaccination surveillance study (N = 409, 59% were vaccinated). Participants completed a questionnaire and were tested for cervicovaginal HPV DNA. HPV prevalence rates were compared in the pre-versus postsurveillance studies by using x 2 tests. Propensity score weighting was used to balance differences in covariates between the 2 surveillance studies. RESULTS:The mean age was ∼19 years for both groups of participants and most were African American and non-Hispanic. After propensity score weighting, the prevalence rate for vaccine-type HPV decreased substantially (31.7%-13.4%, P , .0001). The decrease in vaccine-type HPV not only occurred among vaccinated (31.8%-9.9%, P , .0001) but also among unvaccinated (30.2%-15.4%, P , .0001) postsurveillance study participants. Nonvaccine-type HPV increased (60.7%-75.9%, P , .0001) for vaccinated postsurveillance study participants.CONCLUSIONS: Four years after licensing of the quadrivalent HPV vaccine, there was a substantial decrease in vaccine-type HPV prevalence and evidence of herd protection in this community. The increase in nonvaccine-type HPV in vaccinated participants should be interpreted with caution but warrants further study.

Declining Rates of High-Grade Cervical Lesions in Young Women in Connecticut, 2008–2011

“…These findings are consistent with results from the studies in the United States and other countries that may reflect early vaccine impact (8)(9)(10)(11)(12). For example, Australia has observed dramatic declines in genital warts among women under 21 years of age from 18.6% to 1.9% during 2007 to 2011 and in high-grade cervical abnormalities among women under 18 years of age from 0.80% to 0.42% before and after 2007 (10,11).…”

“…Bauer and colleagues showed a 35% decrease in genital warts among women younger than 21 years of age (from 0.94%-0.61%) between 2007 and 2010 using a family planning administrative database in California (8). Kahn and colleagues estimated a reduction in prevalence of vaccine-type HPV infections from 32% to 13% during 2006 to 2010 among young women recruited from primary care clinics (9). Similar findings have been reported from other countries (10)(11)(12).…”

Distribution of Vaccine-Type Human Papillomavirus Does Not Differ by Race or Ethnicity Among Unvaccinated Young Women

“…[16][17][18] Race was defined as black, white, or other, and ethnicity was defined as Hispanic and non-Hispanic. Each woman also provided a cervicovaginal swab for HPV DNA testing, which was performed using the Roche Linear Array Assay, a PCR amplification/detection system that uses pooled L1 primers and a reverse-line blot detection step to identify 36 different HPV genotypes (Roche Molecular Systems, Alameda, CA).…”

“…Black women were more likely than white women to be positive for ‡1 HPV type (odds ratio [OR] 1.83, 95% CI 1.30-2.58) and Hispanic women were less likely than non-Hispanic women to be positive for ‡1 HPV type (OR 0.47, 95% CI 0.24-0.92). However, among all young women and HPV-infected women, neither race nor ethnicity was associated with positivity for HPV types targeted by the following vaccines: 2-valent (HPV16 and/or 18), 11,16,and/or 18),11,16,18, 31, 33, 45, 52, and/or 58). Conclusion: The prevalence of HPV types targeted by the 2-valent, 4-valent, and 9-valent vaccines did not differ by race or ethnicity among all and among HPV-infected women in this sample.…”

Immunogenicity and Safety of a 9-Valent HPV Vaccine

“…12 The quadrivalent HPV (6/11/16/18) virus-like particle (qHPV) vaccine is highly efficacious in preventing infection and cervical, vaginal, vulvar, and anal dysplasia caused by HPV 6/11/16/18 as well as HPV 6/11-related condyloma, [13][14][15][16] and the bivalent HPV (16/18) vaccine is highly efficacious against HPV 16/18-related infection and cervical dysplasia. 17 Postlicensure studies have shown a rapid decrease in the incidence of high-grade cervical abnormalities, [18][19][20][21] prevalence of vaccine HPV types, [22][23][24][25][26] and incidence of genital warts [27][28][29][30][31] in vaccinees. Data have shown that prophylactic HPV vaccination is generally safe and well tolerated.…”