Two types of HPV linked to cervical cancer have declined since the advent of the HPV vaccine

Bottom Line: An badysis of precancerous cervicals over a seven-year period has shown that two strains of human papillomavirus (HPV) targeted by vaccination since 2006 have decreased, representing a lower proportion of cervical diseases. The study offers evidence that vaccination against HPV reduces the incidence of infections that can lead to cervical cancer

Journal in which the study was published: Cancer epidemiology, biomarkers and prevention, a review of the American Association for Cancer Research.

Author: Nancy McClung, PhD, RN, Epidemic Intelligence Services Officer at the Centers for Disease Control and Prevention (CDC) in Atlanta.

Background: "Almost all badually active people will get HPV at some point in their lives, but most HPV infections will go away without any treatment," said McClung. "If HPV infection does not go away, it can result in cellular changes that, over time, turn into a cervical lesion called precancer cervical precancers." Observe the impact of HPV vaccination earlier than cervical cancer, take decades to develop. "

Previous research has suggested that the incidence of cervical precancer has decreased. In this study, researchers sought to determine whether HPV types 16 and 18, responsible for about 70% of cervical cancers worldwide, were also decreasing. Both types were targeted by the quadrivalent HPV vaccine, which was most commonly administered in the United States between 2006 and 2015, and by the 9-valence vaccine, which is the only vaccine currently administered in the United States.

Study design: As part of the CDC (HPV-IMPACT) Human Papillomavirus (HPV) Vaccine Impact Monitoring Project, McClung and colleagues badyzed more than 10,000 archived specimens collected between 2008 and 2014 from women aged 18 to 39 who had been diagnosed. with cervical intraepithelial neoplasia grade 2 or 3 or adenocarcinoma in situ (CIN2 +). Both are precancerous conditions that may result from persistent HPV infection and may lead to cervical cancer. The researchers tested the samples for 37 types of HPV and then badyzed the proportion and estimated number of cases by HPV types over time.

Results: The researchers found that the number of CIN2 + cases reported to HPV-IMPACT decreased by 21%, from 2,344 in 2008 to 1,857 in 2014. The estimated number of cases attributed to HPV16 / 18 decreased, from 1,235 in 2008 to 819 in 2014.

Among vaccinated women, the proportion of CIN2 + positive for HPV 16/18 increased from 55.2% to 33.3%. In unvaccinated women, the proportion of CIN2 + positive for HPV 16/18 increased from 51.0% to 47.3% and those with unknown vaccine status from 53.7% to 45.8%. %.

Author comments: McClung explained that some vaccinated women were most likely positive for HPV 16/18 because they had been infected with these types of HPV before being vaccinated. The majority of women vaccinated in this study received the vaccine in their early twenties, after the age when most women began badual activity.

McClung said the decline of unvaccinated women may be due to "herd protection," which occurs when a large proportion of the population has developed immunity to an infectious disease, making its spread less likely. Herd protection can be provided by vaccination or by the immunity created by a previous infection, she explained.

The researchers found that each age group experienced a significant decrease in the proportion of positive CIN2 + cases for HPV 16/18, with the exception of the oldest group, the 35-39 years. McClung said this finding reflects the fact that most of these women were not eligible for vaccination because of their age.

In addition, while non-Hispanic whites and blacks experienced a decline in the proportion of positive precancers for HPV 16/18, Hispanic and Asian women were not. McClung said that Hispanic and Asian women included in this study were perhaps less likely to be vaccinated. However, as of 2016, the rate of HPV vaccination was robust among Hispanic and Asian adolescents; therefore, racial and ethnic disparities are expected to be mitigating, McClung said.

The most recent statistics from the CDC show that 49.5% of girls and 37.5% of boys aged 13 to 17 comply with all recommended doses of the HPV vaccine. McClung said clinicians should continue to strongly recommend HPV vaccine to all pre-adolescents at the age of 11 or 12 and respond effectively to common questions parents have about the vaccine.

McClung said that, overall, the study indicated that efforts to encourage families to get HPV vaccines for their teens were bearing fruit and should be pursued.

"This clearly shows that the HPV vaccine works to prevent cervical disease in young women in the United States," said McClung. "In the years to come, the impact should be even greater as more women are vaccinated in early adolescence and before exposure to HPV."

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Limitations of the study: McClung said that one of the limitations of the study was the inability to confirm the vaccination status in about 50% of the women in the study.

Funding and Disclosure: This study was funded through a cooperation agreement under CDC's Emerging Infections program. The authors do not declare any conflict of interest.

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