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Home » Gardasil 9 safety – more published evidence supporting the HPV vaccine

Gardasil 9 safety – more published evidence supporting the HPV vaccine

Two new articles (plus an editorial) published in Pediatrics reinforce the evidence supporting Gardasil 9 safety. I have been writing about the safety of the cancer-preventing HPV vaccines for years, and it’s clear that it’s settled science.

Of course, I’m here to review any new articles about Gardasil 9 safety, because the evidence supporting it has become overwhelming. Nevertheless, HPV vaccine uptake has remained stubbornly low, around 49% in the USA as of 2017. 

Let’s start with a quick review of HPV and HPV vaccines.

Photo by Melissa Askew on Unsplash

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.

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.

Gardasil 9 safety – first paper

The first paper, from researchers at the Centers for Disease Control and Prevention (CDC), was published in November 2019 in Pediatrics. The researchers searched through the Vaccines Adverse Event Reporting System (VAERS) database for US reports of adverse events (AEs) after a 9-valent HPV vaccination from December 2014 (when the 9-valent vaccine was first marketed in the USA) through December 2017.

VAERS is a self-reporting system for adverse events post-vaccination. Utilizing this database as a method to make claims about the lack of safety of a vaccine is prone to abuse. In fact, the website itself states the following with respect to the accuracy of the data:

While very important in monitoring vaccine safety, VAERS reports alone cannot be used to determine if a vaccine caused or contributed to an adverse event or illness. The reports may contain information that is incomplete, inaccurate, coincidental, or unverifiable. In large part, reports to VAERS are voluntary, which means they are subject to biases.

This creates specific limitations on how the data can be used scientifically. Data from VAERS reports should always be interpreted with these limitations in mind.

That being said, it can be used as an “early warning radar” to warn scientists of potential issues, called safety signals.  

The CDC researchers examined three years of this data and found the following:

  • VAERS received 7,244 reports after Gardasil 9 vaccination.
  • 31.2% of the reports were females, 21.6% were males, and 47.2% were unreported gender.
  • 97.4% of reports were nonserious. The most common of these nonserious events included dizziness, fainting, headache, and injection site reactions were most commonly reported – these are fairly common for almost every vaccine.
  • T most commonly reported AEs were similar between females and males.
  • Two reports of death after the 9-valent HPV vaccine were verified. The autopsy reports or death certificates did not suggest a causal relationship with the vaccine.
  • Approximately 28 million Gardasil 9 doses were distributed during the study period – the AE reporting rates were 259 reports per million 9-valent HPV vaccine doses distributed for all reports and 7 per million doses distributed for serious reports. 

The researchers concluded:

No new or unexpected safety concerns or reporting patterns of 9vHPV with clinically important AEs were detected. The safety profile of 9vHPV is consistent with data from prelicensure trials and from postmarketing safety data of its predecessor, the quadrivalent human papillomavirus vaccine.

In addition, the study revealed that several conditions that are claimed to be related to HPV vaccines rarely appeared in VAERS reports. These include postural orthostatic tachycardia syndrome (POTS), complex regional pain syndrome (CPRS), and autoimmune disorders. In particular, POTS and autoimmune disorders have been claimed to be linked to HPV vaccines. Those links have been debunked numerous times. 

Gardasil 9 safety – second paper

The second paper, by Dr. James G Donahue, was also published in November 2019 in Pediatrics. This study examined data from the Vaccine Safety Datalink (VSD), which collects electronic health data from eight healthcare systems across the USA. 

This database includes important information on vaccines – the kind of vaccine given to each patient, date of vaccination, and other vaccinations given on the same day. The VSD also tracks information on medical illnesses that have been diagnosed at doctors’ offices, urgent care visits, emergency department visits, and hospital stays. 

This tracking allows researchers to find potential safety signals in an unbiased and scientific manner between vaccines and potential adverse events.

The researchers examined data from 105 weeks between October 2015 and October 2017. This time frame included 838,991 doses of the 9-valent HPV vaccine. 

The researchers identified “unexpected safety signals” for 4 adverse events:

  • appendicitis among boys 9 to 17 years old after dose 3;
  • pancreatitis among men 18 to 26 years old;
  • allergic reactions among girls 9 to 17 years old and women 18 to 26 years old after dose 2.

The researchers further evaluated these signals and did not confirm that these were actual signals and were classified as false positives. In addition, the lack of biological plausibility and temporal association between these events and the 9-valent HPV vaccination did not indicate causality.

The authors concluded:

With this large observational study, we contribute reassuring post-licensure data that will help bolster the safety profile of 9vHPV. We documented nearly 839 000 9vHPV doses administered over 2 years and did not identify any new safety concerns. Although we detected several unexpected potential safety signals, none were confirmed after further evaluation. Our findings are consistent with pre-licensure clinical trials, which have determined that 9vHPV, similar to 4vHPV, has a favorable safety profile.


In an accompanying editorial about Gardasil 9 safety, H Cody Meissner, MD at Tufts School of Medicine, wrote in Pediatrics:

Wherever vaccination campaigns against vaccine-preventable cancers have launched, the rates of the pre-cancerous cervical lesions related to the human papillomavirus (HPV) have been reduced.

For many generations, people have wished for a vaccine that would offer protection against cancer.

Curiously, such a vaccine is now readily available but reluctance to administer or to accept the vaccine has kept HPV immunization rates far below those of other routinely recommended vaccines.

The time has come for all vaccine administrators and parents to understand that the availability of the 9-valent human papillomavirus vaccine (9vHPV) is one end of a remarkable journey of discovery and progress to develop a safe and effective vaccine to prevent suffering and death from common cancer. 

There are so few ways to prevent cancer – the HPV vaccine is one of the best choices for young men and women. Get the vaccine!

By the way, I wonder what the anti-vaccine zealots are going to do with this data. They love VAERS to support their wild pseudoscientific claims about vaccines. Now, we have real scientists who have used VAERS to establish that the HPV vaccine is safe. Can you imagine the busted irony meters?



Michael Simpson

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