• 5/15/2007
  • Minneapolis, MN
  • Shari Roan
  • StarTribune.com

With human papillomavirus, girls and women have been getting all the attention.
Parents nationwide have rushed to have their daughters vaccinated against the virus. States are wrestling with whether to require that adolescents be vaccinated. And recent research found that many more girls and women are infected with human papillomavirus than was previously thought — more than one-quarter of females ages 14 to 59.

Now the attention is turning to boys and men.

As many as 60 percent of men ages 18 to 70 are infected with HPV, according to data not yet published, raising the question of whether the new vaccine will be effective in reducing diseases linked to the virus unless men, not just women, are immunized.

Several studies are underway to better understand the virus in males and whether the new HPV vaccine, Gardasil, also will work for them. As researchers already know and as the new data confirm, HPV is not just a women’s issue.

“With any transmittable disease, you want to understand the entire cycle of how things spread,” says Thomas Broker, an HPV expert and professor of biochemical and molecular genetics at the University of Alabama in Birmingham. “With HPV, men are clearly part of that equation.”

Human papillomavirus is best known for causing cervical cancer, with about 9,700 cases diagnosed in women nationwide each year.

Gardasil, a three-shot regimen, was approved last year for girls and women ages 9 to 26. It protects against four strains of the HPV virus that are most likely to cause cervical cancer and genital warts in women.

But much less is known about the consequences of HPV infection in men.

“We know they transmit it to women, but what is the rate of transmission?” says Anna Giuliano, a researcher at the H. Lee Moffitt Cancer Center and Research Institute in Tampa, Fla., who is leading three government-funded studies on HPV infection in men. She is also a paid speaker for Merck, maker of Gardasil.

Several studies are attempting to address this question, as well as ones about which strains of HPV are most common in men. New data show that HPV infection is quite common in men of all ages, while the highest rates of infection in women tend to occur in the early 20s before declining and then spiking again in women in their 40s and 50s.

“We’re seeing a really high prevalence in men, and we see little change in prevalence across the age span,” says Giuliano, who found the 60 percent prevalence rate in one of her studies. “We need to know if women in their 40s and 50s are acquiring new infections from their partners.”

A global problem

HPV infection isn’t inconsequential in men. Certain strains of the virus are known to cause genital warts in men as well as women.

And those infections are estimated to be the cause of about half of all anal, penile, vulvar and vaginal cancers and about 20 percent of all oral cancers, says Dr. Dean Blumberg, an associate professor of pediatric infectious disease at the University of California, Davis. Blumberg is a member of Merck’s speakers bureau but is not paid directly by Merck for his services.

About 28,000 Americans learn that they have an oral cancer each year, and about 4,650 receive diagnoses of anal cancer. Penile cancer affects about 1,500 men each year. Although the overall risk of those diseases is low, anal cancer in gay and bisexual men has been rising in recent years.

Worldwide, the consequences of HPV infection in both men and women are even more severe than in the United States, notes Broker, president of the nonprofit International Papillomavirus Society.

More women in developing countries die of cervical cancer than in the United States, he says. Moreover, “we need to know how much real disease men are getting. If you look worldwide, there are about 100,000 new cases of penile cancer each year.”

HPV-related cancer is also more common in people with compromised immune systems, such as men who are HIV-positive.

“This virus can cause cancers in a lot of different places,” Blumberg said. “But in terms of numbers, it doesn’t compare to the number of cervical cancer cases.”

Vaccine differs with men

But even if reducing rates of cervical cancer was the single goal of HPV vaccination, some experts suggest that herd immunity — vaccinating everybody to reduce circulation of the virus in the population — would be the most successful approach.

“If you decrease HPV infection in men, then there will be decreased transmission to women also,” Blumberg says.

Merck is studying the vaccine’s ability to prevent infection in boys and men. Data on those trials might become available this year, and the company hopes to apply to market Gardasil to boys and men next year.

Studies of Gardasil show that the vaccine provokes an even stronger immune response in boys than in girls, which implies that the vaccine also will prevent HPV infections, Blumberg said. But they have yet to show that boys are protected from HPV infection at satisfactory rates. Researchers are also examining whether the vaccine reduces cases of anal cancer in gay men.

There is “no guarantee” an HPV vaccine will work in men, Broker said, because the skin cells infected by the virus differ greatly in men and women.

Debate continues

Some people aren’t waiting for the results of those studies. High-risk men, such as gay and bisexual men, are reportedly requesting and receiving Gardasil vaccination from their physicians, Blumberg said.

Moreover, he says, “I’ve had nurses tell me they made sure their 15-year-old son was vaccinated because they wanted to decrease the chance of their future daughter-in-law having cervical cancer. They felt strongly about it.”

Meanwhile, GlaxoSmithKline plans to seek Food and Drug Administration approval soon for its HPV vaccine for girls and women, Cervarix.

Legislation requiring California girls to complete HPV vaccination before entering seventh grade was introduced recently. Another bill was proposed that would require health insurers to cover the cost of the vaccinations.

Lawmakers in as many as 20 other states have introduced similar proposals. But mandatory vaccination of school-age girls has generated controversy because some parents believe their daughters will not be exposed to the virus or that having the vaccination might encourage sexual activity.

Others object to mandating vaccination for something that is not easily transmitted (unlike chickenpox or measles) and because the shots are costly, about $360 for the series.