HPV vaccine is unrelated to venous blood clots in another huge study

gardasil-retro-advertAnecdotally, it has always seemed like the HPV quadrivalent vaccine, known as Gardasil or Silgard, was the most despised vaccine on the market. Although I write about almost every vaccine, I seem to write more about Gardasil, countering all kinds of silly claims. Despite several large case-controlled epidemiological studies, some of which I’ve discussed previously, there is some pervasive fear that the HPV vaccine is dangerous. You don’t know how many times I’ve read “I vaccinate my kids, but never that Gardasil stuff.”

Just for review, forget that Gardasil saves lives by preventing cancer. The HPV quadrivalent vaccine specifically targets human papillomavirus (HPV) subtypes 16 and 18, that cause not only approximately 70% of cervical cancers, but they also cause most HPV-induced anal (95% linked to HPV), vulvar (50% linked), vaginal (65% linked), oropharyngeal (60% linked) and penile (35% linked) cancers. It also targets HPV6 and HPV11, which account for approximately 90% of external genital warts. The viruses are generally passed through genital contact, almost always as a result of vaginal, oral and anal sex.

There is substantial clinical evidence that once a population is vaccinated against HPV, the rates of infection drop, which should lead to lower risk of various cancers. There is no other way to say this but Gardasil is very safe and very effective at preventing cancers.

But science is irrelevant, if you can spread fear. The antivaccination cult at GreenMedInfo, home of the vaccine denying lunatic Sayer Ji, cherry-picked a whole laundry list of “peer-reviewed”, many of marginal if not laughable quality, trying to “prove” that Gardasil is dangerous. One article, of slightly better quality, use a bit of dumpster diving into the fairly useless VAERS database that showed an overabundance of reporting of venous thromboembolic events, though, because of the quality of data, they authors were unable to establish any firm correlation between the HPV quadrivalent vaccine and those events.

A recent article in the Journal of the American Medical Association does an outstanding job in refuting the hypothesized link between Gardasil and venous thrombi (which can be dangerous). The study examined a population of over 1.6 million women in Denmark, of which just over 500 thousand were immunized with the quadrivalent HPV vaccine. The researchers found 4375 cases of venous thromboembolic events (VTE), of which 3486 did not receive the vaccine, while 889 were vaccinated.


The incidence ratio of vaccinated to unvaccinated was 0.77, which though not statistically significant, meaning that with regards to VTE, it’s safer to get the vaccine than to not. As opposed to pseudoscience pushers, I know that there’s no plausibility to an anti-thromboletic effect of Gardasil, so let’s just accept that the risk of VTE is about the same between vaccinated and unvaccinated groups.

The authors concluded that:

Our results, which were consistent after adjustment for oral contraceptive use and in girls and young women as well as mid-adult women, do not provide support for an increased risk of VTE following quadrivalent HPV vaccination. Two previous studies reported a potential association but one was based on reports from a passive surveillance system and the other included few vaccinated cases, many with known risk factors for VTE.

I know that another huge study that shows that a claimed “risk” is unrelated to the HPV quadrivalent vaccine is not going to change any minds. But once again, those of us who are pro-science (and by extension, pro-vaccine) have overwhelming evidence, in a study of over 1.6 million women, that Gardasil is safe, and it is one of the best methods to prevent a deadly cancer. I just hope some people listen.

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Lifetime lover of science, especially biomedical research. Spent years in academics, business development, research, and traveling the world shilling for Big Pharma. I love sports, mostly college basketball and football, hockey, and baseball. I enjoy great food and intelligent conversation. And a delicious morning coffee!

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  • Another important problem with the use of this vaccine is that it leads to an association between teen girls and sex. Many conservative religious groups view giving the vaccine as giving their teenage daughter license to have sex. This mentality is very similar to the push for abstinence only education. Perhaps we need a PSA aimed at religious organizations to help get past this perception?

    • lilady R.N.

      How silly is that belief about giving teens tacit approval to have sexual relations? You’ve got to be pretty gullible to have that belief about your children.

      Some of those parents may not feel comfortable discussing responsible, safe sexual contacts…so they avoid the discussion completely and deny their children the protection of a safe vaccine.

      About that license…do teens immediately seek out cow pastures strewn with rusty nails to run barefoot…after receiving their Tdap booster vaccines?

  • Dorit Reiss

    I agree that the HPV vaccines have an undeserved bad rep, and it’s tragic: an infection that kills thousands a year and causes tens of thousands of cancers, an effective and safe vaccine.

  • Gardasil – no link. Air travel, especially in coach seats – definite link. Let’s ban air travel. Works for me!

    Actually, most cases of VTE are associated with inactivity and advanced age, along with poor health (cancer and circulatory difficulties). As you would expect. The JAMA article segments the VTE cases by age and excludes those using, for instance, birth control, since hormones can be associated with increased risk.

    “Venous thromboembolism (VTE) occurs for the first time in ≈100 persons per 100,000 each year in the United States, and rises exponentially from <5 cases per 100,000 persons <15 years old to ≈500 cases (0.5%) per 100,000 persons at age 80 years. " http://circ.ahajournals.org/content/107/23_suppl_1/I-4.full

    That is, it is pretty sparse amongst young people. Since the vaccine is given primarily to young people, you would expect to see an increase in the occurrence of VTE in that group if there were any effect. That would be where the anti-vaccination people are looking, I guess. This is a very large universe, though, with many possible candidate causes, so the study that uses just VTE cases narrows the question down to just Does it or Doesn't it, with a definitive It Doesn't.

    • Like I wrote, actually the vaccinated group has a lower incidence of VTE. Though I would never make the claim, because statistically this study wasn’t set up to examine the effect. It’s funny how the anti-vaxxers would jump all over bad numbers if it was in their favor. They’re such scientific morons.

      • They can’t just be morons. There must be a little bit of evil in there too. They actually cause the spread of disease. And why would they expend so much energy if they were just morons?

        • People are stupid; given proper motivation, almost anyone will believe almost anything. Because people are stupid, they will believe a lie because they want to believe it’s true, or because they are afraid it might be true. People’s heads are full of knowledge, facts, and beliefs, and most of it is false, yet they think it all true. People are stupid; they can only rarely tell the difference between a lie and the truth, and yet they are confident they can, and so are all the easier to fool.

          People need an enemy to feel a sense of purpose. It’s easy to lead people when they have a sense of purpose. Sense of purpose is more important by far than the truth. In fact, truth has no bearing in this. They want to believe, so they do.