SAN DIEGO – Young adult women who received the human papillomavirus (HPV) vaccination were less likely to adhere to the recommended screening schedule for cervical cancer, according to a recent study.

In looking at a cohort of women who received at least two Pap smears during a 4-year study period, Daniel Terk, MD, and his colleagues saw a significant drop-off in screening visits after women received their HPV vaccinations. The group of women who received their vaccine midstudy were significantly less likely to come in for annual screening after their vaccination than before (n = 140, adjusted odds ratio 0.19, 95% confidence interval, 0.08-0.49).

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“When following individual vaccinated women, they were five times less likely to be adherent to cervical cancer screening after HPV vaccination,” Dr. Terk said at the annual clinical and scientific meeting of the American College of Obstetricians and Gynecologists. “This may represent an unintended consequence of HPV vaccination.”

The retrospective chart review looked at rates of cervical cancer screening and HPV vaccination across 943 patient charts, beginning in 2006 when the HPV vaccine was released and ending in 2010. The inclusion criteria ensured that “participants were old enough to obtain cervical cancer screening and young enough to receive the HPV vaccine,” Dr. Terk and his collaborators wrote in the research abstract.

The drop-off in adherence for the subgroup who received their vaccines midstudy was an isolated finding, said Dr. Terk, noting that vaccination status did not affect adherence to the recommended screening schedule for the group as a whole.

Billing data and medical records were used to track HPV vaccination status and dates of administration, as well as the dates of testing and results for cervical cancer screening. Patients were included if they were born from 1980 to 1988, if they had two or more Pap smears during the study period, and if their HPV vaccination status could be verified. Patients with an initial abnormal Pap smear or a prior loop electrosurgical excision procedure were excluded, as were patients whose HPV vaccination status could not be confirmed.

In all, 943 patient charts were included in the review; 448 patients had no documented vaccination, with further review showing that 418 of these had, in fact, not been vaccinated, while the remaining 30 had actually had at least one HPV vaccine dose during the study period. Of the 495 patients with at least one documented vaccination, 175 had at least one Pap smear done before they were vaccinated, while 320 had their HPV vaccine before any documented cervical cancer screening.

Thus, there were two patient groups: 593 “unvaccinated” patients, who had at least one cervical cancer screening before receiving the vaccine, and 350 “vaccinated” patients, who had their HPV vaccine before any documented Pap smears.

Dr. Terk and his colleagues considered a screening interval of 18 months or less appropriate, while a longer interval than that between Pap smears was considered inappropriate timing. Individual patients were considered adherent if 76%-100% of their Pap smears were appropriately timed, partially adherent if 50%-75% of their Pap smears were appropriately timed, and not adherent if less than 50% of their Pap smears were appropriately timed.

Of those receiving their vaccine midstudy, 116 (82.9%) were adherent before vaccination, while 69 (49.3%) were adherent after vaccination.

The HPV vaccine is highly effective at preventing infection with the strains of HPV that are primarily responsible for cervical cancer. At the same time, about 70% of the cervical cancer cases that occur are associated with missed screening or inappropriate screening intervals, so screening is still an important part of the strategy to prevent cervical cancers, said Dr. Terk, a 4th-year ob.gyn. resident at the University of Rochester, N.Y.

The ACOG guidelines for cervical cancer screening have shifted through the years. During the period from 2003 to 2009, annual Pap smears were recommended for women under the age of 30 years, beginning at age 21 or 3 years after first sexual intercourse. Women 30 years and older who were at low risk could have a less frequent screening interval. ACOG currently recommends Pap testing alone every 3 years for women aged 21-29 years; co-testing with a Pap test and an HPV test every 5 years in women aged 30-65 years, or a Pap test alone every 3 years.

The study had a large sample size, and adherence rates track with national data, Dr. Terk said. However, screening guidelines have shifted in recent years, and vaccinations are now happening at a much younger age, so the findings should be interpreted with some caution. Still, he said, clinicians should incorporate a strong message about the importance of cervical cancer screening in their HPV vaccination and well-woman counseling.

Dr. Terk reported having no relevant financial disclosures and reported no outside sources of funding.

koakes@frontlinemedcom.com

On Twitter @karioakes

Cervical cancer screening adherence drops after HPV vaccination