New study adds weight to call for boys to get HPV vaccine too

Should boys be vaccinated against human papillomavirus (HPV) alongside the girls?

That’s what Harald zur Hausen (right), the German scientist who was awarded the 2008 Nobel Prize for medicine and a 2008 Gairdner award for discovering the virus's link to cervical cancer, said on a speaking tour of Ontario universities last month. “It’s really important also to vaccinate young men,” he said in a University of Western Ontario release. “Clearly you should protect your partner to not put your partner at risk... Why not have better effects by having more persons vaccinated?”

Besides the potential benefit of reducing the transmission risk, Dr zur Hausen said, protecting boys from HPV infection could also protect them from contracting related cancers. Last year, in a review article in the journal Cancer, a team of researchers from Houston, Texas, came out strongly in favour of vaccinating boys for that very reason. “[W]e fear that vaccination programs limited to females will only delay the potential benefit in prevention of HPV-16/18-associated oropharyngeal cancers, which typically occur in men,” they wrote. “We encourage the rapid study of the efficacy and safety of these vaccines in males and, if successful, the recommendation of vaccination in young adult and adolescent males.”

Well, the first study on the HPV vaccine for boys has finally arrived, although some experts are likely to find it disappointing.

Yesterday, Merck released interim results of a clinical trial that is testing the vaccine on 4,000 HPV-free men between the ages of 16 to 26. (Merck is the manufacturer of Gardasil, the only HPV vaccine cleared for use in Canada, approved only for girls. Another vaccine, Cervarix, made by GlaxoSmithKline, is under review for approval by Health Canada.) Though the trial’s results haven’t been published in a peer-reviewed journal yet -- they were presented yesterday at a conference of the European Research Organization on Genital Infection and Neoplasia, in Nice, France -- the data at a three-year follow-up are encouraging in terms of the vaccine’s effectiveness at preventing genital lesions and genital warts. Only three of the 2,000 patients who received the vaccine got genital warts, compared to 31 in the control group. The vaccine also decreased the viral load in patients already infected with HPV by up to seven times more than the control.

“The study is still ongoing, but we're relieved to know that it is as effective in men as it is in women,” Dr François Coutlée, a University of Montreal microbiologist who recruited patients in Montreal for the Merck-funded trial, told Canwest News Service.

However, the study failed to show any effect on cancer rates in boys. None of the trial participants were diagnosed with penile, perineal or perianal cancers by the end of the study. Three patients in the control group were diagnosed with potentially precancerous lesions, compared to zero in the vaccinated group, but those numbers are too small to be meaningful. (It’s not clear why Merck didn’t include oropharyngeal cancers in its study, as the Texas team had hoped.) The study’s failure to demonstrate the vaccine’s effect on cancer is a function of the same problem that some critics of the HPV vaccine identified in the trials on girls: the trials’ follow-up periods aren’t long enough to determine whether there will actually be a drop in cancers, and, if so, how long the vaccine’s protection will last.

“Men can unknowingly transmit HPV to their partners, putting them at risk for developing HPV related disease - most notably, cervical cancer in women. HPV can also cause penile and anal cancer in men, as well as genital warts,” Merck spokesperson Tracy Ogden told Canadian Medicine. “Merck is pursuing an indication in males aged 9-26 and plans to submit a regulatory application to the Food and Drug Administration later this year.”

Photo: Nobelprize.org

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