Confusion surrounds HPV vaccine for men
Should men routinely receive the vaccine for human papillomavirus (HPV) that protects against cervical and anal cancers and warts? Those hoping for a clear answer will have to settle for something less, at least for now.
The federal Food and Drug Administration approved Gardasil for use in women in 2006 to protect against four types of HPV that cause the vast majority of cancers and warts. It waited for completion of a trial in gay men to give the nod for that indication on October 16 of this year.
But a week later, on October 23, a Centers for Disease Control and Prevention advisory committee said Gardasil should not be added to the recommended list of vaccines for all pre-teens. That is important because the vaccine is most effective if it is given before one becomes sexually active.
The decision came on the heels of an analysis in BMJ, once the British Medical Journal, that said use of the vaccine in all men was not cost effective. The authors did concede that it might be cost effective in specific higher risk groups such as gay men.
At the same time, Dr. Peter Chin-Hong, a researcher at the University of California, San Francisco, published a paper showing, "The more HPV types you had, the greater your likelihood of becoming infected with HIV."
The analysis was drawn from the three-year Explore study of 1,409 gay men in Boston, New York, Denver, and San Francisco. It appeared in the journal AIDS.
There are two reasons why sexually transmitted diseases increase the risk of acquiring HIV: first, they cause a breakdown in the physical barrier of the skin and second, all infections stimulate an immune response that attracts CD4 cells and macrophages, which are the primarily cells that HIV targets.
"That has long been known for sexually transmitted diseases such as syphilis and gonorrhea, but nobody has looked at HPV, perhaps because it is so common," Chin-Hong said in an interview.
"Almost 100 percent of people get exposed to HPV in their lifetime," Chin-Hong said. "If you are not HIV-positive there is about a 20 percent chance of detecting HPV at any one time, and a 10 to 20 percent chance it will go on to have persistent infection - finding the same HPV type twice in the same year."
Many infectious diseases generate a strong systemic immune response and once recovered, the person is protected against subsequent infections. But HPV infection usually generates a modest and localized immune response; only about 40 percent of people show even low levels of antibodies in their blood. That does not protect against reinfection or infection at another location.
"At some point the probability is that HPV is going to get into the right place at the right time, set up shop, and if it is a high risk type virus, it will integrate into your DNA and over time could develop into cancer," Chin-Hong said.
Chin-Hong said that the vaccine is different from a natural exposure to HPV in that it creates a robust systemic immune response in nearly 100 percent of people that protects against infection and reinfection.
There also is some evidence that the stronger response not only protects against the four types of HPV contained in the vaccine but also offers some cross-protection against other HPV types.
He believes that people who are already sexually active may benefit from the vaccine "because there is a chance that they have not been exposed" to all of the different types of HPV.
Anal cancer cells
Among HIV-negative gay men, the rate of anal cancer is "as high as cervical cancer in women before the introduction of Pap smears. And if you are HIV-positive, it's about double that," Chin-Hong said.
Women suffer from lower rates but higher total numbers of anal cancer than do gay men. Actress Farrah Fawcett died of anal cancer that had metastasized but few people knew that detail because of the taboo surrounding anal sex.
Regularly screening gay men for HPV precancerous anal lesions and removing them has proven to be as effective as Pap smears and interventions for cervical cancer in containing the disease. UCSF has developed a good screening program, but few doctors around the country are trained in the procedure or are comfortable with issues of anal health.
"If money were not an issue, I would say that everyone should get the HPV vaccine. I would like to take it myself," said Chin-Hong. But it comes down to money; he is waiting to see if his health provider will cover the cost of the three-shot vaccine series.