Atlanta ? A vaccine against cervical cancer also prevents other types of gynecological cancers and could lower the incidence of tumors in the head and neck, too, according to a new study released Sunday.

“If we vaccinate everybody in the U.S., we could probably impact head and neck cancer in approximately 20 years,” said Marshall R. Posner, an associate professor at Harvard Medical School and medical director of the head and neck oncology program at Dana-Farber Cancer Institute in Boston.

On Sunday, researchers at a cancer meeting in Atlanta released data showing that Gardasil, manufactured by Merck & Co., was 100 percent effective in preventing vaginal and vulvar cancers associated with the human papillomavirus, or HPV, in more than 18,000 women and adolescents from the United States, South America and Asia.

For the study, researchers gave females ages 15-26 up to three doses of the vaccine over a six-month period and followed them for two years. None of the women who received the vaccination developed HPV-related vaginal or vulvar precancers, compared with 24 women in the control group.

“In human disease, there has never been a vaccine this effective,” said Jorma Paavonen, professor and chief in the department of obstetrics and gynecology at the University of Helsinki in Finland, who presented the study.

“It’s going to make a major impact and we certainly hope, in the future, this vaccine will be part of the national vaccine program, not only in the U.S., but elsewhere in the world,” he said.

HPV causes cervical cancer and genital warts and is linked to penile and anal cancer. The virus is the most common sexually transmitted disease, and the American Cancer Society estimates that HPV affects more than 50 percent of sexually active adults.

Last month, a U.S. Food and Drug Administration advisory committee recommended approval of Gardasil. The FDA is not required to follow the recommendations of its outside panels of experts but usually does. An agency decision is expected as early as today.

The vaccine, however, needs to be given before a person has sexual contact because it’s not going to work optimally if people already have been exposed to the virus.

“We’ll have a huge hill to climb to convince parents to vaccinate their 12- or 13-year-old boys or girls,” said Vanessa Barnabei, professor of obstetrics and gynecology at the Medical College of Wisconsin and Froedtert.