There are dozens of types of HPV, including more than 40 that can be transmitted sexually. Some can cause cancer. Two vaccines, Merck’s Gardasil and GlaxoSmithKline’s Cervarix protect against two types of cancer-causing HPV. Both vaccines are approved and recommended for girls and young women. Gardasil is also recommended for boys up to age 18 since its protection extends to two additional types of HPV that cause genital warts in males and females.
It’s widely assumed that limiting the virus in men or women would diminish its spread in the whole population. But while HPV has been extensively studied in women, its prevalence is less well understood in men, says Joseph Monsonego of the Institute of the Cervix in Paris, writing in the same Lancet issue. For that reason, he says, the new study results “are of substantial interest.”
Starting in 2005, epidemiologist Anna Giuliano of the H. Lee Moffitt Cancer Center & Research Institute in Tampa, Fla., and an international team of researchers recruited more than 4,000 men living in Brazil, Mexico and Florida into a study of HPV. The new study reports on the first 1,159 of these volunteers. Their average age was 32 and none had been vaccinated against HPV. Swabs of the penis and genital area of each man revealed that 50 percent were infected with at least one HPV type upon enrollment.
The researchers repeated these exams every six months, and the men completed personal-history questionnaires. Over a median of 28 months, the group acquired 1,572 new HPV infections.
The human immune system can clear HPV out of the body, and the men wiped out most of their new infections during the study period. But it took a median 7.5 months. Median clearance times didn’t vary substantially among the countries, but did vary between HPV types. Some cases lingered as long as 24 months in the men.