STD Awareness: Human Papillomavirus Grabs Headlines

Human papillomavirus, or HPV, is the most common STD out there — a fact made even more aggravating by the absence of a good test for it. Sure, Pap testing can detect cellular abnormalities triggered by HPV, and the HPV DNA test can find evidence of infection. But it’s not a definitive test — a negative Pap/HPV DNA co-test doesn’t rule out the possibility that you carry the virus. Ditto for the anal Pap test — which most people haven’t even heard of anyway!

There are more compelling reasons to vaccinate boys against HPV — and not-as-compelling reasons to think Gardasil could protect against skin cancer.

The lack of a good diagnostic test makes the HPV vaccine an even more valuable asset. If we can drive the virus to extinction through aggressive vaccination campaigns, our limited diagnostic abilities become a moot point. And recent headlines have given us reasons to love the HPV vaccine even more.

HPV and Men

Many people think of HPV as a women’s issue, as the virus causes cervical cancer, and for a long time, boys and men weren’t even targeted for vaccination. But HPV is everyone’s issue — genital warts don’t care what gender you are, and cancer-causing strains of HPV cause most cases of anal cancer, penile cancer, and oropharyngeal cancer. Recently, a large, first-of-its kind study published in JAMA Oncology analyzed penile swabs provided by 1,757 men to figure out how common HPV is in this population. (While there is no FDA-approved test for diagnosing male patients with HPV, scientists can still collect swabs for research purposes.)

The results: 45.2 percent of American men ages 18 to 59 carry genital HPV — for a total of nearly 35 million adult males. HPV carriers can transmit the virus to sexual partners through vaginal, anal, or oral sex — or even just rubbing genitals together, as the virus is spread by skin-to-skin contact. Furthermore, a quarter of men are infected with cancer-causing strains of HPV. And, while the female population sees a peak in HPV infections in their early 20s, men’s HPV prevalence increases with age. While 28.9 percent of men 18 to 22 years of age carried HPV, 50.8 percent of them carried it by the time they were 28 to 32 years of age, and 59.7 percent of 58- and 59-year-olds were carriers.

For now, it’s a mystery why HPV prevalence increases as men age. It could be that they have a weaker immune response, and either are more likely to develop chronic infections or less able to develop an immune memory, leaving them more vulnerable to reinfection. If men’s immunological memories are weaker, they could possibly benefit from vaccination even after becoming sexually active, as it’s thought that the vaccine creates a stronger immune memory than does a natural infection.

It’s a shame that, of men who weren’t too old to receive the vaccine when it was approved, only 10.7 percent had been vaccinated. The strong vaccine-induced immune memory might help protect men from HPV infections well into adulthood, protecting their female partners from exposure to HPV strains that cause cervical cancer — and protecting everyone from those that cause anal cancer, oropharyngeal cancer, and genital warts.

HPV and Skin Cancer

Recently, the HPV vaccine made headlines for its apparent ability to protect against skin cancer. But not so fast! Whereas the study of HPV in men included nearly 2,000 participants, this “study,” published in JAMA Dermatology, looked at a whopping two patients. The authors described two elderly adults prone to keratinocyte carcinomas, the most common type of skin cancer, of which there are two subtypes: squamous cell carcinomas (SCC) and basal cell carcinomas (BCC). After receiving all three doses of Gardasil over a six-month period, the first patient saw a 62.5 percent reduction in SCC, while the second patient saw a 66.5 percent reduction — and neither patient developed BCC.

A sample size of two doesn’t even count as a study, and is more appropriately called a case report — and case reports have been fodder for ridiculous rumors about the HPV vaccine in the past, such as the myth that it can cause infertility. When you’re only looking at one or two people, it’s difficult — even impossible — to make assumptions about cause and effect. Having said that, there is one thing about this recent publication that makes it more intriguing than other rumor-generating case reports, and that is what’s called “biological plausibility.” Cancer-causing HPV strains are known to disrupt DNA repair and make it harder for the immune system to get rid of defective cells — and, while UV light is the primary culprit behind skin cancers, previous studies have shown an association between certain HPV strains and skin cancer.

Here’s the lowdown on the diversity of HPV, whose different strains wreak a variety of havoc: Some HPV strains cause genital warts, while others cause genital cancers. Other strains infect different areas of the skin and might make sunburned skin more vulnerable to cancer. Although Gardasil doesn’t target HPV types associated with skin cancer, vaccination might help the immune system recognize other HPV strains, providing protection beyond just the target HPV types — including, possibly, skin-cancer-associated HPV strains.

If you’re like me — genetically at a dramatically higher-than-normal risk for skin cancer and aspiring to a vampire lifestyle in order to avoid the sun’s sinister forces — you might leap at the chance to be vaccinated against a type of skin cancer. And as much as I want to believe the sensationalist headlines, I shouldn’t rush out to get Gardasil 9 just yet. While the results are interesting, they’re far from a smoking gun, and simply provide a starting point for other researchers to test the hypothesis in large clinical trials. If Gardasil actually protects against keratinocyte carcinomas, that would be the icing on the cake of an already fantastic vaccine — but an even more exciting prospect is the development of an HPV vaccine specifically targeting the strains associated with the most common types of skin cancer, which might help make them less common.

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