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Home » Gardasil safety facts – debunking myths about the HPV vaccine

Gardasil safety facts – debunking myths about the HPV vaccine

I’ve written nearly a metric tonne of articles about Gardasil safety facts over the past eight years. Most of my posts covered peer-reviewed studies and meta-reviews that support the overall HPV vaccine safety and effectiveness profiles. It is settled science

There are so many myths, memes, and tropes about HPV vaccine safety, all of them based on anecdotes, false claims, and stories – all of them lack the support of robust scientific evidence. 

For example, there have been several recent stories about the claimed dangers of the HPV vaccine, like Colton Berrett’s tragic suicide after contracting transverse myelitis. The parents blamed Gardasil for Colton’s disease, despite the fact that there is simply no evidence of such a link. Of all of the vaccines on the market, the anti-vaccine world appears to reserve their most unscientific hatred for Gardasil.

There is one common point about my boatload of articles about Gardasil safety facts – they are backed by literally dozens of powerful, unbiased, statistically significant, repeated clinical and epidemiological studies. 

Gardasil safety facts

All about HPV vaccines

Many of you have read this section an enormous number of times, however, for some of the readers of this blog, this article might be their first bit of research into the human papillomavirus (HPV) vaccine. Thus, it’s important to get a brief overview of HPV and the vaccines. If you’ve read this section before, just skip to the next section if you want.

Genital and oral  HPV infections are the most common sexually transmitted infections (STI) in the USA.  HPV is generally transmitted from personal contact during vaginal, anal or oral sex.

It’s important to note that there are more than 150 strains or subtypes of HPV that can infect humans – however, only 40 of these strains are linked to one or more different cancers. Although the early symptoms of HPV infections aren’t serious and many HPV infections resolve themselves without long-term harm, HPV infections are causally linked to many types of cancers in men and women. According to current medical research, here are some of the cancers that are linked to HPV:

These are all dangerous and disfiguring cancers that can be mostly prevented by the HPV cancer vaccine. If you’re a male, and you think that these are mostly female cancers, penile cancer can lead to amputation of your penis. Just think about that guys.

HPV is believed to cause nearly 5% of all new cancers across the world, making it almost as dangerous as tobacco in that respect. According to the CDC, roughly 79 million Americans are infected with HPV – approximately 14 million Americans contract a new HPV every year. Most individuals don’t even know they have the infection until the onset of cancer. Accordingly, over 31,000 HPV-related cancers are diagnosed in the USA every year.

There were two HPV vaccines on the world market before 2014. GSK, also known as GlaxoSmithKline manufactured Cervarix, a bivalent vaccine. It has been withdrawn from the US market (although available in many other markets), because of the competition from the quadrivalent (immunizes against four different HPV subtypes) and 9-valent (against nine subtypes) Gardasil vaccines.

Merck manufactures Gardasil, probably the most popular HPV vaccine in the world. The first version of the vaccine, quadrivalent Gardasil, targets the two HPV genotypes known to cause about 70% of cervical cancer and two other HPV genotypes that cause genital warts. In Europe and other markets, Gardasil is known as Silgard.

The newer Gardasil 9, approved by the FDA in 2014, is a 9-valent vaccine. It targets the four HPV genotypes in the quadrivalent version, along with five additional ones that are linked to cervical and other HPV-related cancers. Both versions of Gardasil are prophylactic, meant to be given before females or males become exposed to possible HPV infection through intimate contact.

Gardasil is one of the easiest and best ways to prevent a few deadly cancers that are related to HPV. It is definitely a cancer-preventing vaccine.

(Just a quick note. There are actually two cancer-preventing vaccines. Along with the HPV vaccines, the hepatitis B vaccine is also important for the prevention of some cancers.  The vaccine prevents hepatitis B viral infections. Chronic hepatitis B infections can lead to liver cirrhosis or cancer. Liver cancer is actually one of the few cancers in the USA where the incidence has increased over the past few years. And if you follow the anti-vaccine rhetoric, you know the hepatitis B vaccine is almost as controversial as the HPV vaccine.)

Currently, in the United States, the Advisory Committee on Immunization Practices (ACIP) recommends that preteen girls and boys aged 11 or 12 are vaccinated against HPV. The immunization is also recommended for teenage girls and young women up to the age of 26 who did not receive it when they were younger, and teenage boys and young men up to the age of 21.

Real math is used to analyze real science. Photo by John Moeses Bauan on Unsplash

All about Gardasil safety facts

I want to forestall the logical fallacies employed by the anti-vaccine forces. Science works in one way – review all of the high-quality published evidence, then develop a conclusion based on that evidence. Science deniers, who make up the bulk of the anti-vaccine world, believe that one should create a conclusion, then scan the internet for cherry-picked evidence to support that a priori conclusion.

Importantly, there are plenty of published articles of robust evidence derived from huge epidemiological studies that have established solid Gardasil safety facts – that is, there are no established links between Gardasil and many serious adverse events. The internet abounds with stories that Gardasil caused this or that, yet if we look at the clinical evidence, we never see it. And dumpster diving into the VAERS database is not useful in telling us anything about Gardasil safety facts.

As I mentioned, there are literally dozens of outstanding published clinical or epidemiological studies that support the safety of the HPV vaccine. Since I don’t want to write a 50,000-word article (and I know some of you would read it, respect), I decided to choose the six with the largest number of participants that give the most powerful results.

No this isn’t cherry-picking, because I’m not ignoring articles that support the anti-vaccine beliefs. Actually, there are no clinical or epidemiological studies that support any of the false claims about Gardasil. 

Photo by Clem Onojeghuo on Unsplash

Six studies that support Gardasil safety facts

A large study of 790,000 Danish women who received the HPV vaccine found no increased risk of demyelinating diseases, such as transverse myelitis, multiple sclerosis, and other diseases compared to non-vaccinated Danish women. The authors concluded that,

In this study with nationwide coverage of 2 Scandinavian countries, qHPV vaccination was not associated with the development of multiple sclerosis or other demyelinating diseases. These findings do not support concerns about a causal relationship between qHPV vaccination and demyelinating diseases.

Another large study of over 1 million women found no safety signals for autoimmune diseases, neurological and venous thromboembolic (venous blood clots) events in HPV vaccinated women. The researchers deduced that,

This large cohort study found no evidence supporting associations between exposure to qHPV vaccine and autoimmune, neurological, and venous thromboembolic adverse events. Although associations for three autoimmune events were initially observed, on further assessment these were weak and not temporally related to vaccine exposure. Furthermore, the findings need to be interpreted considering the multiple outcomes assessed.

A recent meta-review (considered the pinnacle of biomedical research) of over 100 different safety studies of the HPV vaccine, that included over 2.5 million individuals, found no increased risks of adverse events of special interest (AESI), which are events that can cause serious harm. The authors of this study concluded that,

There was no consistent evidence of an increased risk of any AESI, including demyelinating syndromes or neurological conditions such as complex regional pain or postural orthostatic tachycardia syndromes. The risk-benefit profile for HPV vaccines remains highly favourable.

A peer-reviewed CDC study of 8 years of HPV-vaccine clinical and epidemiological studies found no serious adverse events including TM. Their review of Gardasil safety facts found that,

In the United States, post-licensure vaccine safety monitoring and evaluation are conducted independently by federal agencies and vaccine manufacturers. From June 2006 through March 2014, approximately 67 million doses of HPV4 were distributed in the United States, and from October 2009 through March 2014, a total of 719,000 doses of HPV2 were distributed. Overall, HPV4 has accounted for approximately 99% of doses distributed since 2006. Multiple studies have provided evidence supporting HPV vaccine safety

A study of over 3 million Scandinavian women found no link between the vaccine and demyelinating diseases. The authors stated the following conclusion:

In conclusion, our study of serious adverse event rates in qHPV (quadrivalent Gardasil)-vaccinated and qHPV-unvaccinated adult women 18-44 years of age did not raise any safety issues of concern.

There are at least 10 other large-scale clinical and epidemiological studies that reject the hypothesis of serious adverse events linked to HPV vaccines. These studies included over hundreds of thousands or millions of patients. They are sufficiently powered so that they could potentially uncover even the rarest of adverse events. Yet, they found little to nothing.

Again, if we go with the scientific method of analyzing a question, reviewing all of the highest quality evidence, it is difficult to ignore the Gardasil safety facts – the cancer-preventing vaccine is extraordinarily safe. In fact, because it was developed way after other vaccines, it may be one of the safest vaccines ever marketed.

Quack. Quack. Photo by Chandler Cruttenden on Unsplash

Cherry-picking Gardasil safety facts

I know some people reading this article who hate Gardasil will cherry-pick studies from pseudoscientists Shaw, Tomljenovic, Shoenfeld (and more recently here), and Exley – these papers have either been published in low impact factor predatory journals, been retracted, or been roundly rejected by the scientific community.

When I say we must “review all of the highest quality evidence,” these studies don’t qualify. They are not large-scale epidemiological studies. They are not even small-scale human clinical trials. They are poorly done studies that attempt to find anything to support the pre-ordained conclusion that something is wrong with Gardasil. They are, at best, “opinions” which are absolutely not scientific facts.

In addition, these “researchers” try to examine other components of the vaccine, specifically the aluminum adjuvant, to claim that it has some causal effect on neurodegenerative diseases. Notwithstanding the tiny subclinical amount of aluminum in the HPV vaccines, there is almost no evidence that the aluminum in vaccines is related to any neurological condition.

Two of the huge proponents of this myth about Gardasil are the aforementioned Shaw and Tomljenovic, whose articles about aluminum in HPV vaccines and neurodegenerative diseases have been highly criticized and retracted. And of course, the World Health Organization publicly discredited the claims of these two, making many of us wonder why they continue to have research positions at their home, the University of British Columbia. But that’s another story.

On the other hand, we have robust and statistically powerful studies of millions of people where we can find no statistical signal of a link between the HPV cancer-preventing vaccine and any serious adverse event. Even when we went looking really hard for some evidence of anything that may cause us to be concerned about the vaccine.

Furthermore, Gardasil-haters will try to claim that the vaccine got some special treatment from European and American drug regulators. That myth is so easily debunked that I wonder why the vaccine haters haven’t taken that off their list of standard copy-pasted remarks on any vaccine comment thread.

One more thing – determining causality between Gardasil and any claimed adverse event requires passing a test of biological plausibility. We need to know if there is a reasonable biological pathway from the injection of the vaccine to the claimed event. Relying on special pleading and magical thinking to create this pathway is not convincing – you need some solid scientific evidence to support plausibility.

Gardasil safety facts – conclusion

I can only go with the evidence, and it’s nearly overwhelming – Gardasil is an extraordinarily safe medicine. Huge post-licensure case-control studies have shown us that there aren’t even weak signals for adverse events that could be related to the vaccine.

We have ample evidence that Gardasil prevents at least seven types of cancer. We have vigorous evidence that Gardasil is impressively safe. Unless someone wants to deny either of those points, because they don’t like scientific research, we can only conclude that the benefits of Gardasil far outweigh the risks.

We have looked carefully at the Gardasil safety facts – we found that it is one of the best and safest cancer prevention tools.


This article was originally published on January 2018. It has been updated to include more studies, to copyedit, and to add more nonsense from the HPV vaccine-haters. 




Michael Simpson

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