I was sent a link to this article that appeared July 18, 2013 in the New York Times. It has a very catchy headline:

HPV Vaccine Found to Help With Cancers of the Throat

Wow, I thought. Really? How is this possible?

First of all, we do know that HPV is responsible for an every growing number of throat cancers. We also know that smoking is a co-factor, number of oral-sex partners (that’s how you catch oral HPV), and specifically being male.

The HPV vaccine is very effective at reducing the viral burden in the genital tract, so many have 20081218.153734_cervarixpresumed/hoped that this would eventually pay off in a benefit for oral cancers. But note I say eventually. HPV-related head and neck cancers among men occur most typically in the 40-59 years age group.

But here’s the issue, the HPV vaccine is approved for girls as young as 9 years old and up to the age of 26 and it was only approved in the United States in 2006, although granted it had been studied for many years before that. What I’m getting at is if the HPV vaccine reduces oral cancer, isn’t it a little early to actually see that effect considering the age where that cancer shows up is 40? Especially in a study that lasted 4 years?

I went over to PLOS One and looked at the study, entitled Reduced Prevalence of Oral Human Papilloma Virus (HPV) 4 Years After Bivalent Vaccination in a Randomized Clinical Trial in Costa Rica.

This is study of only women ages 18-25, so not the high-risk group for oral HPV-related cancers.

Acquisition of oral cancer was also not a study end point.

So, while the study is fascinating in that the presence of HPV DNA was lower in both the mouth and the cervix of vaccinated women compared with controls, this does not draw any conclusion remotely close, to the vaccine has been “found to help with cancers of the throat.”

HPV infected squamous cells
HPV infected squamous cells

You have to have HPV in the mouth at some point to get an HPV-related cancer, this is true. However, as this is study of women we can not make any assumption that vaccinated males will be less likely to have HPV in the mouth. Hormones and many other factors affect HPV acquisition and persistence. We can also not draw the conclusion that reducing HPV carriage in the mouth will reduce HPV-realted oral cancers. It seems intuitive, but to 18th Century physicians it was intuitive to treat multiple maladies with leeches. The point is, even if it seems like there is a ton of indirect evidence supporting something, you often need direct evidence to make a statement of fact. This is one of those times.

The article itself does a good job of reporting that this study was women, not men. It also points out that 4 years (the length of the study) is not long enough to know if reducing HPV in the mouth or cervix affects oral cancer risk (kind of refuting the title right there). The NYT article also mentions other risk factors for throat cancer, so another plus.

However, early on in the article there is a troubling statement: Oncologists have assumed that the human papillomavirus vaccine, which is used to prevent cervical cancer, would also prevent this other type of cancer, but this was the first study to provide evidence.

This study from Costa Rica, as interesting and well-done as it is. It provides data on reduction of oral HPV post vaccination against types 16 and 18 (essentially the title of the study) and it is encouraging. It tells us further studies are needed, but it provides no evidence that the vaccine reduces throat cancer. The title and some of the content in the New York Times article is simply misleading. Whether that represents a misunderstanding on the part of the reporter or an overzealous copy editor, I don’t know. But it’s wrong and a correction is in order.

There is a lot of misinformation about vaccines and it behooves us all to stick to the truth.

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  1. Jen, I want to provide some clarifications for the next time you right about HPV-linked oral cancers.

    1) While tobacco and alcohol use are linked to oral cancer as well, the growth in HPV-linked oral cancers is most clearly seen among those who do not use tobacco and use alcohol at levels below where it is considered a risk factors.
    2) While oral sex may seem to be logically linked to HPV-linked oral cancer, the research is not so clear. What is clear is that those with more than 6 sex partners are more likely to get an HPV-linked oral cancer. Until more data is collected on lifetime sexual experience, HPV-linked oral cancer needs to be associated with sexual activity and not just oral sex.
    3) Oral cancers are increasingly being identified prior to treatment as being HPV-linked or not HPV-linked. This information is used to determine treatment as well as survival probabilities. Cancers that are identified as HPV-linked have a much higher survival rate, although treatment is still quite harsh.
    4) Part of the problem with doing studies on the efficacy of an HPV vaccine on oral cancers is the length of time between onset of an HPV infection and the diagnosis of Oral cancer. The first long term study (10 years) indicates that 1/3 of all throat cancers are linked to HPV virus. See: http://www.medicalnewstoday.com/articles/263741.php It is likely that this share will rise as the study extends into its 2nd decade. Given the average age of the patient when an HPV-linked oral cancer is diagnosed. It is possible that we have yet to see the full impact of the spread of HPV two to three decades ago.
    5) HPV-linke oral cancers are much more common among men than women. I have not seen any studies looking at heterosexual vs. homosexual men which is why the link between HPV-linked oral cancer and any sexual activity is week. So the beneficiaries of vacination would be mostly men and the length of time between HPV infection and cancer diagnosis is longer than any pharma would be willing to run a study prior to marketing.

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