HPV vaccine protects against low-grade lesions

The human papillomavirus (HPV) vaccine substantially reduces the incidence of low-grade neoplasia and genital warts (condyloma) for more than three years after vaccination, according to a new study.

The data were gathered from two international randomized, controlled trials of the quadrivalent HPV vaccine (Gardasil) conducted by the vaccine manufacturer. The trials included more than 17,000 women ages 16 to 26. Participants were excluded for a history of more than four sexual partners, abnormal cervical smear test results or pregnancy. They were given three doses of the vaccine (which targets HPV types 6, 11, 16 and 18) or placebo. The follow-up was continued for 42 months, and the study was published online by BMJ on July 21.

Among participants who tested negative for the relevant HPV types at the start of the study, the vaccine was almost totally effective against lesions caused by HPV type 6, 11, 16 or 18: 96% effective for cervical intraepithelial neoplasia grade I, 100% for vulvar and vaginal intraepithelial neoplasia grade I and 99% for condyloma. When lesions caused by other HPV types were included, the vaccine's effectiveness was substantially lower. Overall, it was 30% effective at preventing cervical neoplasia grade I, 75% for the vulvar type, 48% for vaginal and 83% for condyloma.

The study had a longer follow-up period than previous research, the study authors noted. The vaccine's efficacy against low-grade lesions is important because these occur far more often than higher-grade lesions, and prevention can reduce patient anxiety, morbidity and health care costs, the authors noted. The control group of the trial also allowed the researchers to estimate the overall incidence of condyloma in unvaccinated women, which they put at 1% per year.