Receiving two doses of human papillomavirus (HPV) vaccine at 5-month intervals or longer appears to provide similar protection against genital warts as three doses among girls initiating the series before age 15 years, reported Rebecca B. Perkins, MD, of Boston University, and her associates.

Of 387,906 adolescent females, 8% received 1 dose of HPV vaccine, 9% received 2 doses, 31% received 3 doses, and 52% remained unvaccinated. The mean age of the girls in the study was 15 years, and average length of follow-up was 6 years. The girls were aged 9-18 years on Jan.1, 2007, and the exposure period began at that time for unvaccinated girls or on the date of the last HPV vaccine injection for those receiving the vaccine. Among girls receiving more than 1 dose, 60% received their second dose within 3 months of their first dose (on time), and 47% received their third dose within 5 months of their second dose.

The overall rate of genital warts was 1.97/1000 person years. The rate of genital warts declined with added HPV vaccine doses: 2.17 cases/1,000 person years for unvaccinated girls, 1.90 cases/1,000 person-years for girls receiving 1 dose, 1.76 cases/1,000 person-years for girls receiving 2 doses, and 1.5 cases/1000 person-years for girls receiving 3 doses. Receiving 3 doses was significantly more efficacious than 0 or 1 dose, but the difference between 2 and 3 doses was not significant. The incidence rate of genital warts was similar whether girls completed 2 doses at less than 5-month intervals or at longer than 5 months. Unvaccinated girls had nearly double the risk of genital warts, compared with girls who completed the series (incidence rate ratio, 1.90). Girls who had 1 dose of HPV vaccine had fewer genital warts than unvaccinated girls, but more than the girls who completed the series (IRR, 1.22).

“Although reductions in genital warts are an important early marker of vaccine effectiveness, reductions in cervical dysplasia and cancers are far more important vaccine-related outcomes,” Dr. Perkins and her associates said. “Human papillomavirus vaccine protection must last many years to provide adequate cancer protection, therefore ongoing studies are paramount,” they noted.

The study used data from the Truven Health Analytics MarketScan Commercial Claims Database, covering enrollees and dependents from about half of provider-sponsored U.S. health insurance plans.

Read more at (Sex Transm Dis. 2017 Jun. doi: 10.1097/OLQ.0000000000000615 ).


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