Three new studies add to a growing body of research showing that men and boys vaccinated against the human papillomavirus (HPV) are much less likely than others to be infected with the ubiquitous virus, which can cause cancers of the head and neck, anus, and penis, as well as genital warts.

• A randomized trial from Japan, published in The Lancet Infectious Diseases earlier this month, found that Gardasil 9—which protects against nine HPV strains—dramatically reduced the risk of developing anal or genital HPV infections. The vaccine prevented 92% of persistent infections with the most common strains of HPV and 73% caused by strains that are less common but still able to cause cancer. The researchers followed more than 1,000 men for a median of 2.4 years.
• A real-world study from Canada, published in The Journal of Infectious Diseases yesterday, focused on gay and bisexual men ages 16 to 23. The study of nearly 1,200 men confirmed that HPV vaccination is most effective when given at a young age, before people are exposed to the virus. Men vaccinated by age 23 were 60% less likely to have anal HPV infections than others in the study. The researchers found no reduction in HPV risk among men vaccinated at age 27 or older.
• A review of 21 studies performed from 2007 to 2024, published in The International Journal of Infectious Diseaseslast week, found that HPV vaccinations prevent anal, penile, and oral infections in men. Studies included Gardail 9, as well as an earlier vaccine that prevented four HPV strains. While results varied from study to study, researchers from University of Florida and Merck Research Laboratories found that evidence suggests that vaccines provide good protection, ranging from a 51% reduction in the risk of penile HPV infections to a 100% reduction in the risk of oral HPV infections. Merck is the manufacturer of Gardasil 9.

“It’s exciting,” Neil Gross, MD, director of clinical research in the department of head and neck surgery at MD Anderson Cancer Center, told CIDRAP News when asked about the new findings.

“We’ve known vaccination is the right thing to do,” said Gross, who was not involved in the studies. “That’s why HPV is recommended as a gender-neutral vaccination strategy. It’s nice to see some data quantifying the benefit.”

Good news for men and public health

HPV affects about 80% of sexually active women and more than 90% of men. A small number of people develop persistent HPV infections, which can lead to cancer. HPV spreads through intimate contact, including vaginal, anal, and oral sex, and even deep kissing. 

The randomized, controlled trial from Japan “demonstrates that there is real-world, personal benefit to HPV vaccination for boys and men,” said Demetre Daskalakis, MD, MPH, chief medical officer at the Callen-Lorde Community Health Center in New York, which provides LGBTQ health care.

“Vaccination prevented persistent infections which can be associated with cancers… regardless of the gender of sexual partners,” said Daskalakis, former director of the Centers for Disease Control and Prevention’s National Center for Immunization and Respiratory Diseases.

The systematic review also “re-affirms the observation that the HPV vaccine is good for public health by interrupting the chain of sexual transmission,” said Daskalakis, who was not involved in the new research.

The studies illustrate why it’s important to vaccinate people before they are sexually active, Daskalakis said. The American Academy of Pediatrics recommends boys and girls begin the HPV vaccine series at ages 9 to 12 years.

“Planning for HPV cancer prevention is like packing an umbrella before the rain starts,” Daskalakis said. “We know that most people will eventually become sexually active, so it’s smartest to prepare before the exposure happens.”

Evidence to change vaccine policy

In the United States, the Food and Drug Administration (FDA) approved HPV shots for girls in 2007 and for boys in 2011. 

About 78% of teens have received one or more doses of the vaccine, although only 63% have received all recommended doses. Children receive two to three doses of the HPV vaccine, depending on the age at which they’re first vaccinated.

Planning for HPV cancer prevention is like packing an umbrella before the rain starts.

At least 85 countries now offer HPV vaccines to both boys and girls. But there are huge gaps in coverage. The World Health Organization (WHO) estimates that none of the boys in the Eastern Mediterranean and Southeast Asia have completed the three-dose HPV vaccine regimen, while only 1% of boys have in the African and Pacific regions.

Although Japan approved HPV shots for boys in 2020, the vaccines are not yet part of the country’s recommended and subsidized routine vaccination program.

Taito Kitano, DrPH, a researcher at Nara Prefecture General Medical Center in Nara, Japan, described the new studies as “important evidence indicating the beneficial impacts of HPV vaccination in males.”

Kitano, who also was not involved in the new studies, said, “these data explain why we are recommending HPV vaccination in boys, as well.”

In a review published in April, Kitano and his colleagues found that vaccination was linked to a nearly 50% drop in the risk of any HPV-related cancer in men.

Because HPV-related tumors can take decades to develop, there are relatively few studies showing changes in cancer or even pre-cancer rates. Given the results of studies like those published this year, many experts predict that future studies will also find that HPV vaccines protect men from anal, penile, and oral cancers.

Although research shows that HPV vaccination prevents cervical cancer, there is much less evidence about other cancer types. Studying cervical cancer in vaccinated women is easier, because those cancers often develop when women are in their 30s. Head and neck cancers tend to be diagnosed in men in their 60s.

“Vaccination programs started in girls and were implemented later in boys,” wrote Miyuki Sawata, PhD, and Alain Luxembourg, MD, PhD, two of the authors of the randomized trial of Gardasil 9 in Japan, in an email. “It is expected that it will take a few more years to observe a decrease in non-cervical cancers related to HPV in vaccinated populations.”

A randomized trial in China is expected to help answer these questions by 2029. The study will compare rates of anogenital cancers and precancers in vaccinated and unvaccinated men. Another ongoing international trial, scheduled to conclude in 2028, will measure rates of persistent HPV-related oral infections in men vaccinated with Gardasil 9 and in unvaccinated men.

A very common virus

Preventing head and neck cancers is particularly important, because there are no proven ways to screen for these tumors, which can develop deep in the throat or on the back of the tongue, Gross said. Many head and neck cancers are found only after becoming advanced, when harsh treatments are necessary.

“We don’t have a Pap smear for the throat,” Gross said. People with head and neck cancers experience “a big impact on quality of life and function, and the ability to participate in society the way they did before,” he said.

Surveys show that relatively few people have heard of HPV. While more people know that HPV causes cervical cancer, more than 70% are unaware that HPV causes head and neck cancers, now the most common types of cancer caused by HPV.

“I can’t believe that it’s not better known that HPV is associated with head and neck cancers,” said Kevin Conlon, who was diagnosed with HPV-related cancer four years ago, after finding a lump in his neck while shaving. “If the vaccine had been available earlier, I would have encouraged my son to take it.”

We don’t have a Pap smear for the throat.

Conlon encourages people to vaccinate both boys and girls against HPV.

“I hear some of the concerns by some who don’t want their children to be vaccinated,” said Conlon, now 65. “Some are just anti-vaxx on principle, and others worry that having the vaccine will somehow give their children tacit permission to have sex.”

People “need to know that a vaccine is a lot cheaper and a hell of a lot less painful than surgery, chemo, and radiation.”