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Home » HPV vaccine safety study – biased, poor design and results

HPV vaccine safety study – biased, poor design and results

If you want to read a quality HPV vaccine safety study, I can point to numerous high quality, unbiased, well-designed epidemiological studies that show that HPV vaccines are safe and very effective.

Here’s a review of a study of 200,000 subjects.

Here’s a review of a study with over 1,000,000 subjects.

Here’s a review of a study with over 2,000,000 subjects.

If you want to give us a new HPV vaccine safety study, it better have large numbers (to identify small differences in risks), be unbiased, and use some sort of control group.

HPV and HPV vaccines

I know, I’ve written about this vaccine over 100 times – however, this might be your first bit of research into the HPV vaccine, so it’s important to get a brief overview of HPV and the vaccines. If you’ve read this before, just skip to the next section if you want.

Genital and oral human papillomavirus (HPV) are the most common sexually transmitted infections (STI) in the USA. There are more than 150 strains or subtypes of HPV that can infect humans, although only 40 of these strains are linked to a variety of cancers. HPV is generally transmitted from personal contact during vaginal, anal or oral sex.

Although the early symptoms of HPV infections aren’t serious, those infections are closely 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 with respect to cancer. According to the CDC, roughly 79 million Americans are infected with HPV–approximately 14 million Americans contract HPV every year. Most individuals don’t even know they have the infection until the onset of cancer. About 27,000 HPV-related cancers are diagnosed in the USA every year.

There were two HPV vaccines on the market. GSK, also known as Glaxo SmithKline manufactured Cervarix, a bivalent vaccine which has been withdrawn from the US market. Merck manufactures Gardasil9, a 9-valent vaccine, along with Gardasil, a quadrivalent HPV vaccine.

HPV vaccine safety study from Japan

A new study by K Ozawa et al., published in Drug Safety, seemed to indicate that there is a link between the HPV vaccine and numerous serious adverse effects. So why does this study have results that vary greatly from huge studies that show the opposite result? Because the study from K Ozawa et al. is simply not that good, and I’ll show why.

Japan has been in the middle of a Gardasil vaccine controversy for several years. Japan’s Ministry of Health used bad mathematics to withdraw recommendations for Gardasil. This had lead to lawsuits and to the subsequent anti-vaccine false tropes about Gardasil being banned in Japan. I guess the study was in response to the controversies about Gardasil in Japan.

The researchers examined 120 patients and determined that 30 were diagnosed with having definitive vaccines-related symptoms and 42 were diagnosed as probably. At first blush, that might seem like there’s a large number of vaccine-related “symptoms” but a further review of their research would make you wonder what they were trying to show.

Here are some concerns:

  1. It was a very small study of only 120 patients. It is almost impossible to develop proper statistics with such a small number
  2. The population was not chosen at random. There is extremely high bias in the choosing of patients in this study, just on the basis of complaining about post HPV vaccine symptoms.
  3. All 120 patients complained of vaccine related symptoms – this is the epitome of bias.
  4. The average time between vaccination and appearance of symptoms was over 319 days, nearly a year. It is difficult, if not impossible, to tie a medical procedure with an event that happens 319 days later.
  5. The researchers invented their own diagnostic criteria for vaccine related symptoms.

Let me stress once again, that this is a group of 120 patients who complained about HPV vaccine related issues. This wasn’t a random sampling of those who received the vaccine.

Nearly 10 million individuals in Japan have received the vaccine since launch. A proper study would have looked out how those 120 patients relate to the 10 million vaccinated ones. And how do those symptoms in the 120 patients related to a random population of unvaccinated individuals. Large studies, that I mentioned at the top, have shown us that the “symptoms” described in this paper happen at or below the rate of those symptoms in the general population of that age.

Ozawa et al. also present no convincing evidence that these symptoms are related to the HPV vaccine. It’s especially unconvincing that they want us to believe that symptoms that arise nearly a year after vaccination are caused by that vaccination.

Lastly, Ozawa et al. do not present any biological plausibility for a link between these symptoms and the vaccination. One of the important foundations of determining causality is plausibility, and there simply is none here.

HPV vaccine safety study – summary

I suspect that this HPV vaccine study will become a key talking point for the anti-Gardasil crowd, a particularly obnoxious subgroup of anti-vaxxers. But as far as I can tell, this study functions more as a large case study, which sits near the bottom of the hierarchy of scientific evidence, than original research that provides evidence on the safety, or lack thereof, of the vaccine.

This is a highly biased study that examines only patients who have self-described symptoms after the vaccine, up to two years after the vaccination itself. It is not a random sampling of a large population of vaccinated individuals. It does not contain a proper control.

Out of 10 million patients who have received the vaccine, this study represents only 0.0012% of that group. That’s a very low adverse reaction rate, because we actually have no data on how this relates to the general population. And we have no idea whether these “symptoms” have any relationship to the vaccines.



Michael Simpson
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