Trials show that two vaccines are effective against genital cancers and warts

Two separate studies show that Merck & Co.'s and GlaxoSmithKline's human papillomavirus (HPV) vaccines appear highly effective in preventing cervical cancer, vulvar cancer, and genital warts.

The recently completed trials involved Merck's Gardasil and GlaxoSmithKline's experimental vaccine. Earlier studies showed that Gardasil also protects against cervical intraepithelial neoplasia (CIN)—precancerous lesions that can develop into cervical cancer.

In the Gardasil study, 2,261 sexually active women between 16 to 23 years old were vaccinated with a regimen that included additional vaccinations at one and six months. A similar group of 2,279 women were injected with placebo on the same schedule. None of women in the treatment group developed genital warts, high-grade vulvar epithelial intraepithelial neoplasia (VIN) or vaginal intraepithelial neoplasia (VaIN)—whereas 40 cases of genital warts or precancerous lesions occurred among women in the latter group.

In the study of GSK's HPV vaccine, researchers found that vaccinating females 10 to 14 years old resulted in robust seroconversion: Titers were nearly double those of women who were vaccinated between 15 and 25 years old. Researchers note that this finding about seroconversion is critical because HPV infection usually develops within a year of a woman becoming sexually active.

The GlaxoSmithKline vaccine targets two strains of HPV, and is intended to prevent cervical cancer; Merck's Gardasil targets four strains of HPV—aiming at not only cervical cancer but external lesions such as genital warts.