An FDA advisory committee unanimously recommended approval of the first vaccine against human papilloma virus (HPV) on May 18; final approval is expected this week.

HPV is a major cause of vaginal, cervical and anal cancers, as well as warts. More than a hundred different variations of HPV have been identified and linked to specific types of abnormal skin growths.

The viruses can be transmitted through skin-to-skin contact and need not involve penetration. Condoms offer some protection but they do not cover all of the surface area that can transmit or become infected with HPV.

The viruses are extremely common. A majority of people are exposed to some of the strains within five years of becoming sexually active. Some people develop antibodies sufficient to throw off or control the virus, while others develop tissue irregularities that can progress to cancer.

A Pap smear in the female genital tract and a similar procedure in the anus identifies abnormal tissue so that it can be removed before it develops into cancer.

Gardasil is the name of the vaccine that the FDA is reviewing. It protects against infection from two of the most common forms of HPV, which account for roughly 70 percent of cervical cancers, and two other strains that produce about half of all genital warts. It is being developed by the pharmaceutical company Merck.

Worldwide trials in more than 17,000 girls and women have shown that it is nearly 100-percent effective at preventing infection from those four strains of HPV.

The vaccine has no therapeutic effect once someone becomes infected with those four strains of HPV, so it is important that people be vaccinated before or soon after they become sexually active.

That raised the concern that socially conservative groups, with their focus on sexual abstinence until marriage, might oppose approval of the vaccine. Those fears did not pan out; most conservatives have come to support approval so long as vaccination is voluntary and not mandatory.

The focus of HPV study over the years has rightly been on women, while study in men has lagged. University of California San Francisco researcher Joel Palefsky has led the way in studying HPV in gay men.

He initially noted that those infected with HIV were much more likely to develop anal cancer than the national average. Subsequent testing for the presence of HPV in the rectum found rates of infection as high as 85 percent in gay men.

Though most would not develop cancer, it raised the need for regularly monitoring the bottoms of gay men with a variant of the Pap smear, in much the same way that reproductive tracts of women should be monitored. Abnormal growths should be removed before they can develop into cancer.

HPV also is known to cause cancer in the penis and mouth, though it is not a leading cause of cancer in those parts of the body. A recent study in Spain found HPV present in the anus of 83 percent, in the penis of 38 percent and in the mouth of 33 percent of HIV-positive gay men.

“Rates of anal cancer among men who have sex with men are the same as rates of cervical cancer among women before Pap smears became routine, yet most men are unaware of this disease,” said Andrea Krick in an exclusive interview. She coordinates recruitment for the gay men’s trial of Gardasil that is underway in six U.S. cities.

The trial has had greater difficulty recruiting participants than the company had anticipated. Krick said part of the problem is that “girls go to the doctor regularly and guys just don’t.” But it goes beyond that to “just the lack of disease knowledge” of HPV and the risk of cancer, she said.

The study is looking for healthy, sexually active men who self-identify as gay; with a low number of sexual partners; ages 16-26; and who do not have any symptoms of HPV infection. Participants must be willing to commit to the three-shot vaccination program over six months and follow up with researchers for up to three years.

Krick said the gay men who are most likely to be aware of HPV are those who already are infected and have had problems with warts. These men are not eligible for the trial. Advertising has drawn only a limited response. The most effective recruitment has been through talking to small groups of young gay men.

More information on HPV and how to participate in the Gardasil trial is available at http://www.hpvvaccinetrials.com/secure/index.html.