Anecdotally, 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.
- Gee J, Naleway A, Shui I, Baggs J, Yin R, Li R, Kulldorff M, Lewis E, Fireman B, Daley MF, Klein NP, Weintraub ES. Monitoring the safety of quadrivalent human papillomavirus vaccine: findings from the Vaccine Safety Datalink. Vaccine. 2011 Oct 26;29(46):8279-84. doi: 10.1016/j.vaccine.2011.08.106. Epub 2011 Sep 9. PubMed PMID: 21907257.
- Lowy DR, Schiller JT. Prophylactic human papillomavirus vaccines. J Clin Invest. 2006 May;116(5):1167-73. Review. PubMed PMID: 16670757; PubMed Central PMCID: PMC1451224.
- Schiller NM, Pasternak B, Svanström H, Hviid A. Quadrivalent Human Papillomavirus Vaccine and the Risk of Venous Thromboembolism. JAMA. 2014 July 9;312(2):187-8. doi: 10.1001/jama.2014.2198
- Slade BA, Leidel L, Vellozzi C, Woo EJ, Hua W, Sutherland A, Izurieta HS, Ball R, Miller N, Braun MM, Markowitz LE, Iskander J. Postlicensure safety surveillance for quadrivalent human papillomavirus recombinant vaccine. JAMA. 2009 Aug 19;302(7):750-7. doi: 10.1001/jama.2009.1201. PubMed PMID: 19690307.