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Decline in Rates for HPV16/18-Positive Cervical Precancers Since Introduction of the HPV Vaccine

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Key Points

  • Within 8 years since the HPV vaccine was introduced in 2006, there was an overall declining trend in the proportion and estimated number of cervical precancers caused by HPV vaccine types among women aged 18–39.
  • Among women who were vaccinated, the proportion of CIN2+ cases that were HPV16/18-positive declined from 55.2% to 33.3%. Among unvaccinated women, the proportion of CIN2+ cases that were HPV16/18-positive declined from 51.0% to 47.3%, and among those with unknown vaccination status, from 53.7% to 45.8%.
  • The declining proportion of HPV16/18-positive CIN2+ provides additional evidence of vaccine impact in the United States.

According to the World Health Organization, approximately 70% of cervical cancers worldwide are caused by the human papillomavirus (HPV) types 16 and 18. In 2006, the HPV vaccine was introduced in the United States to prevent HPV-associated morbidity and mortality. A study analyzing data on the prevalence of cervical precancers positive for HPV16/18 since the HPV vaccine was introduced in 2006 has found that among vaccinated women aged 18–39 with cervical intraepithelial neoplasia grades 2–3 or adenocarcinoma in situ (CIN2+), the proportion caused by HPV16/18 decreased by 22% between 2008 and 2014. The declining proportion of HPV 16/18-positive CIN2+ provides additional evidence of the impact of the HPV vaccine in the United States. These findings were published by McClung et al in Cancer Epidemiology, Biomarkers & Prevention.

Study Methodology

The researchers analyzed data from more than 10,000 archived specimens collected from women aged 18–39 between 2008 and 2014 as part of the Centers for Disease Control and Prevention’s HPV Vaccine Impact Monitoring Project (HPV-IMPACT). The women had been diagnosed with grade 2 or 3 cervical intraepithelial neoplasia or CIN2+. The researchers tested the archived specimens for 37 types of HPV and analyzed the proportion and estimated number of cases of CIN2+ by HPV type over time. Trends in HPV16/18-positive CIN2+ were examined, overall and also by vaccination status, age, histologic grade, and race/ethnicity using Cochrane-Armitage tests.

Study Results

After analyzing 10,206 archived specimens, the researchers found that the proportion and estimated number of cases of HPV16/18-positive CIN2+ declined from 52.7% (1,235 cases) in 2008 to 44.1% (819 cases) in 2014 (P < .001). Declining trends in the proportion of HPV16/18-positive CIN2+ were observed among:

  • Vaccinated (55.2%–33.3%, P < .001) and unvaccinated (51.0%–47.3%, P = .03) women;
  • Women aged 18–20 (48.7%–18.8%, P = .02), 21–24 (53.8%–44.0%, P < .001), 25–29 (56.9%–42.4%, P <.001), and 30–34 (49.8–45.8%, P = .04) years;
  • CIN2 (40.8%–29.9%, P < .001), and CIN2/3 (61.8%–46.2%, P < .001; and
  • Non-Hispanic white (59.5%–47.9%, P < .001) and non-Hispanic black (40.7%–26.5%, P < .001) women.

“From 2008-2014, the proportion of HPV16/18-positive CIN2+ declined, with the greatest declines in vaccinated women; declines in unvaccinated women suggest herd protection,” concluded the study authors.

The Health Impact of the HPV Vaccine

“This is clear evidence that the HPV decline is working to prevent cervical disease in young women in the United States,” said Nancy McClung, PhD, RN, Epidemic Intelligence Service Officer at the Centers for Disease Control and Prevention (CDC) and lead author of this study, in a statement. “In the coming years, we should see even greater impact as more women are vaccinated during early adolescence and before exposure to HPV.”

Dr. McClung is the corresponding author of the Cancer Epidemiology, Biomarkers & Prevention article.

Disclosure: This study was funded by a cooperative agreement through the CDC’s Emerging Infections Programs. The study authors' full disclosures can be found at cepb.aacrjournals.org.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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