NEW YORK (Reuters Health) - Significant population-level decreases in rates of cervical intraepithelial neoplasia (CIN) occurred among girls and women in their late teens and early 20s following the introduction of the human papillomavirus (HPV) vaccine in 2007, a new study shows.
"Reductions in the incidence were greater than anticipated based on HPV vaccination coverage in the population and the proportions of CIN attributable to HPV types directly targeted by the vaccine (HPV-6, HPV-11, HPV-16, and HPV-18)," researchers note in JAMA Oncology, online September 29.
Mean uptake of all three doses of the HPV vaccine among teen girls in New Mexico increased from 17% in 2008 to 40% in 2014.
The significant population-level decreases in CIN among partially vaccinated cohorts that the researchers observed "suggest a rapidly approaching need to revisit clinical guideline recommendations for cervical cancer screening in the United States, including increasing the age to begin screening," senior author Dr. Cosette M. Wheeler of the University of New Mexico told Reuters Health by email.
Current guidelines, which were updated in 2012, recommend initiating screening for cervical cancer with cytology (Pap testing) in women at age 21 and every three years until age 30; for women ages 30 to 65, the guidelines advise screening with a Pap test every three years or, for those who want to lengthen the screening interval, screening with a combination of cytology and HPV testing every five years (http://bit.ly/2cTFATM).
The new findings "offer the first U.S.-based data that has adjusted for cervical screening, which underwent huge changes, including moving from annual to triennial cervical screening and using HPV testing plus Pap tests," noted Dr. Wheeler. "These changes in screening overlapped with HPV vaccine introduction, which made it much more difficult to estimate vaccine impact."
The researchers used data from the New Mexico HPV Pap Registry, which was established just before the first HPV vaccine was licensed in the United States, to examine population-based trends in cervical screening and to estimate the effect of HPV vaccination. The registry receives mandatory reporting of all cytologic and HPV testing and any cervical, vulvar, and vaginal histopathological findings for all women living in New Mexico.
After adjustments for decreases in cervical screening during the study period, incidence per 100,000 women of all grades of CIN (including low-grade CIN1 and high-grade CIN2 and CIN3) decreased significantly among individuals ages 15 to 19.
CIN1 incidence dropped from 3,468.3 to 1,590.6, CIN2 incidence dropped from 896.4 to 414.9, and CIN3 incidence declined from 240.2 to 0 (annual percentage decreases of 9%, 10.5% and 41.3%, respectively).
The CIN2 incidence rate also declined significantly in women 20 to 24 years, from 1,027.7 to 627.1 (an annual decrease of 6.3%).
The findings suggest that the greater-than-anticipated impact of the HPV vaccine may likely have come from protection of individuals who received only one or two vaccine doses (instead of the recommended three doses) or vaccine cross-protection against some cancer-causing HPV strains not directly targeted by the vaccine. Another factor may have been herd immunity due to decreases of HPV prevalence among both vaccinated females and males, which would lower the probability of being infected, explained Dr. Wheeler.
An HPV vaccine was approved for use in U.S. males in 2009.
In addition to increasing the age to begin screening, the researchers said that screening methods and strategies and algorithms for clinical management "will need to evolve as we work toward a rational integration of HPV vaccination and cervical screening."
The United States does not come to mind as "the champion of high HPV vaccination coverage," especially compared with Australia, the United Kingdom, and Canada, yet "even with its relatively low coverage rates, (it) is already seeing the earliest effects of what we expected of the HPV vaccines," said Dr. Eduardo Franco, of McGill University, in Montreal, Canada.
"As the authors posit, screening will have to start later and perhaps be done less frequently over a lifetime," said Dr. Franco, who was not involved with the current study.
That recommendation and the authors' conclusion that screening and vaccination should be integrated for optimal planning and delivery of health benefits "are music to my ears," he said, explaining that he and colleagues had projected a decrease in the predictive value of approaches to screening that were in place when the vaccine was approved, as vaccination coverage increased and HPV prevalence decreased (http://bit.ly/2dzAmBd).
"Cervical cancer screening will have to change in the era of HPV vaccination," he said. "There were already a number of excellent reasons to change from the old paradigm of cervical cytology to molecular testing for HPV, but vaccination brought a sense of urgency to that."
The study had no commercial funding.
SOURCE: http://bit.ly/2dmuxZt
JAMA Oncol 2016.
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