I have written nearly 200 articles on the HPV vaccine, and the simple conclusions based on the published evidence is that the Gardasil vaccine is safe and extremely effective. This is essentially settled science.
Of course, the anti-vaccine zealots continue to push the narrative that somehow the HPV vaccine causes all kinds of harms, almost all of these claims without merit. In other words, they lack any verifiable and reliable evidence.
On the other hand, researchers continue to examine whether the Gardasil vaccine is safe, and the simple interpretation of that evidence is that the HPV vaccine is incredibly safe, and there is no evidence of major adverse events linked to the vaccine.
Because there is such a large volume of published evidence supporting the fact that the Gardasil vaccine is safe, I thought I would look at the four best, highest-quality published articles that support this claim. Maybe you all can use it when some anti-vaxxer tries to tell you that the HPV vaccine makes some specious claims about its safety.
All about HPV and HPV vaccines
I know I add this section to every article I write about HPV vaccines. It is updated almost every time with additional information about HPV or the vaccine. Moreover, there are new readers who want to know more about HPV, and this section can help someone get up-to-speed quickly. This article will be cornerstone content for Gardasil vaccine safety, so I want to be thorough.
If you’ve read this section 47 times, just skip down to the next section where I discuss the key points of this article.
Genital and oral human papillomavirus (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. Of those 40 strain, most are fairly rare.
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:
In addition, there is some evidence that HPV infections are causally linked to skin and prostate cancers. The link to skin cancer is still preliminary, but there is much stronger evidence that HPV is linked to many prostate cancers.
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. The CDC also states that over 43,000 HPV-related cancers are diagnosed in the USA every year. It may be several times that amount worldwide.
There were two HPV vaccines on the world market before 2014. GSK, also known as GlaxoSmithKline, produced Cervarix, a bivalent (protects against two HPV strains) 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 strains) and 9-valent (against nine HPV strains) 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, protecting against HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58. It targets the four HPV strains found 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 to females or males before they become exposed to possible HPV infection through intimate contact.
Gardasil is one of the easiest and best ways to prevent a few dangerous and, to abuse the definition slightly, common cancers that afflict men and women. Without a doubt, the HPV vaccine prevents cancer.
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.
Let me sum this all up so that if you come away from this section with nothing else, you get this summary. HPV is a sexually transmitted disease. HPV causes 43,000 cancers a year in the USA alone. The HPV vaccine prevents becoming infected by HPV, which means you are protected from these cancers.
Gardasil vaccine is safe – Australia
In a study of adverse effects of Australians who had received over nine million doses of the HPV vaccine over 11 years, researchers found no concerning adverse effects except for syncope, a condition that is frequently observed with all vaccines or procedures that use needles such as blood draws.
In an August 2020 study, published in Vaccine (reviewed here), Dr. Anastasia Phillips, et al. examined Australian surveillance data for quadrivalent human papillomavirus vaccine over 11 years. The researchers analyzed HPV vaccine adverse events as reported to the Australian HPV vaccination register.
During those 11 years, over nine million doses of the HPV vaccine were administered in Australia. Of those, the researchers found 4,551 observed adverse event reports. They determine that there was a crude reporting rate of 39.8 adverse events per 100,000 doses of the vaccines.
They also found that:
- The rate for syncope, or fainting, was 29.6 cases per 100,000 doses in 12-13-year-old males and females during an “enhanced surveillance” period.
- The syncope rate was 7.1 per 100,000 doses in the other surveillance periods.
- The rate of anaphylaxis was about 0.32 per 100,000 doses.
- The researchers found other reported adverse events including autoimmune disease, postural orthostatic tachycardia syndrome (four cases), primary ovarian insufficiency (12 cases with variable times post-vaccination), Guillain-Barré syndrome (four cases), complex regional pain syndrome (four cases), and venous thromboembolism (three cases). However, all of these were reported at extremely low rates, and the authors did not find any unexpected patterns that would suggest a causal association between the vaccine and these adverse events. Moreover, these low numbers are approximately the same as what we would find in a general, non-vaccinated population.
The authors concluded:
Over an 11-year period, reporting rates of AE following 4vHPV
administration in Australia were consistent with data from similar
surveillance systems internationally and did not reveal any new or
concerning safety issues. However, during a period of enhanced
surveillance implemented to monitor introduction of the vaccine
to adolescent males in addition to females, syncope was noted to
occur at a higher rate in younger adolescents than previously
observed. AESI, except for syncope, were reported rarely following
4vHPV and no new or concerning patterns were identified. This
comprehensive analysis further contributes to the large body of
existing data affirming the safe post-marketing profile of 4vHPV
vaccine in both males and females and the value and characteristics of long-term spontaneous reporting systems in monitoring
So, the Gardasil vaccine is safe.
Gardasil vaccine is safe – autonomic dysfunction
Researchers examined patients with autonomic dysfunctions (see Note 1), such as chronic fatigue syndrome, complex regional pain syndrome, and postural orthostatic tachycardia syndrome, and found no link to HPV vaccines.
In a paper published, September 2020, by Anders Hviid et al. in the BMJ (and reviewed here), the researchers wanted to “evaluate the association between quadrivalent human papillomavirus vaccination and syndromes with autonomic dysfunction, such as chronic fatigue syndrome, complex regional pain syndrome, and postural orthostatic tachycardia syndrome.”
The researchers examined 869 patients with autonomic dysfunction syndromes from a cohort of 1.38 million Danish-born females who were aged 10 to 44 years during 2007-16. Of those 869, 136 were diagnosed with chronic fatigue syndrome, 535 with complex regional pain syndrome, and 198 with postural orthostatic tachycardia syndrome. This is one of the largest studies examining links between the HPV vaccine and autonomic dysfunction.
What did the researchers find?
- The HPV vaccine did not statistically increase the risk of all autonomic dysfunction syndromes within 365 days following vaccination. The risk of all syndromes was about 0.99 or nearly the same as non-vaccinated individuals.
- Various time periods post-vaccination did not indicate that there was an increased risk of all syndromes after HPV vaccination.
- The risk of CFS was 0.38 compared to non-vaccinated – in other words, there was actually a much lower risk of CFS in vaccinated individuals.
- The risk of POTS was 0.86 compared to non-vaccinated.
- The risk of CPRS was 1.31 compared to non-vaccinated, which means there was an increased risk of CPRS in the vaccinated group. However, it appears that CPRS post-vaccination is observed with other vaccines as a result of needle trauma. Furthermore, other studies, such as a large Finnish study, have established that the HPV vaccine is actually linked to a lower risk of CPRS.
The authors concluded:
…our study does not support a causal association between quadrivalent human papillomavirus vaccination and chronic fatigue syndrome, complex regional pain syndrome, or postural orthostatic tachycardia syndrome, either individually or as a composite outcome.
Gardasil vaccine is safe – VAERS
Researchers examined over 7,000 VAERS reports after the Gardasil9 vaccine was administered. Over 97% of the reports were classified as non-serious, and no serious events could be causally linked to the vaccine.
The first paper, from researchers at the Centers for Disease Control and Prevention (CDC), was published in November 2019 in Pediatrics (reviewed here) 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 non-serious. The most common of these non-serious events included dizziness, fainting, headache, and injection site reactions were most commonly reported – these are fairly common for almost every vaccine.
- The 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, especially autonomic dysfunction discussed above, rarely appeared in VAERS reports. This study establishes that the Gardasil vaccine is safe.
Gardasil vaccine is safe – VSD
This study examined 839,000 HPV vaccinations reported to VSD and did not find any safety signals.
A study by Dr. James G Donahue, published in November 2019 in Pediatrics 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 that was discussed in the previous two articles, 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.
Gardasil vaccine is safe – primary ovarian insufficiency
This study examined nearly 59,000 women who received the HPV vaccine and found that there was a 70% lower risk of primary ovarian insufficiency compared to unvaccinated women.
In a paper published in Pediatrics (reviewed here), Allison Naleway et al. identified 199,078 females, aged 11-34 years, who were members of Kaiser Permanente Northwest from August 2006 (when Gardasil was first available to Kaiser Permanente members) through the end of 2014, when the study was ended. The researchers used such a large group of females to maximize the number of primary ovarian insufficiency (POI) cases.
The cohort study followed each of these nearly 200,000 female members until they either disenrolled from Kaiser, their 35th birthday (when natural changes in menstrual periods or infertility may start), or the end of the study period, whichever came first.
In the population of nearly 59,000 females who received the HPV vaccine, they found one case of an individual who may have had symptoms of POI after receiving the vaccine. If there were a higher risk of primary ovarian insufficiency in the vaccinated group, we would expect numbers as high as the non-HPV vaccine “control” group, which had 45 cases. In fact, the hazard ratio shows that there is a 70% lower risk in the HPV vaccinated group compared to the unvaccinated group (although we probably shouldn’t make a claim that the HPV vaccine lowers the risk of POI).
The authors concluded that there was no “statistically significant elevated risk” of primary ovarian insufficiency after receiving the HPV. The authors stated that “these findings should lessen concern about POI risk after adolescent vaccination.”
These five, large, robust, peer-reviewed studies show that the Gardasil vaccine is safe. There just isn’t any links between the vaccine and any of the serious adverse events claimed by the anti-vaccine crowd.
As I wrote previously, the HPV vaccine prevents cancer, and we also have superior evidence that it is demonstrably safe.
Get this vaccine for yourself, if you’re in the target age groups, or for your children. It can prevent cancer.
- Anti-vaxxers, especially those whose mission is to reject the fact that the Gardasil vaccine is safe, claim that it is linked to autonomic dysfunction, or dysautonomia, a rather broad term that describes conditions in which the autonomic nervous system (ANS) does not work properly. Some of these conditions, such as chronic fatigue syndrome (CFS), complex regional pain syndrome (CPRS), and postural orthostatic tachycardia syndrome (POTS) are claimed to be caused by the HPV vaccine by anti-vaxxers such as Yehuda Shoenfeld. I’ve debunked any links between the HPV vaccine and POTS and CPRS in the past.
- Donahue JG, Kieke BA, Lewis EM, Weintraub ES, Hanson KE, McClure DL, Vickers ER, Gee J, Daley MF, DeStefano F, Hechter RC, Jackson LA, Klein NP, Naleway AL, Nelson JC, Belongia EA. Near Real-Time Surveillance to Assess the Safety of the 9-Valent Human Papillomavirus Vaccine. Pediatrics. 2019 Nov 18;. doi: 10.1542/peds.2019-1808. [Epub ahead of print] PubMed PMID: 31740498.
- Hviid A, Thorsen NM, Valentiner-Branch P, Frisch M, Mølbak K. Association between quadrivalent human papillomavirus vaccination and selected syndromes with autonomic dysfunction in Danish females: population based, self-controlled, case series analysis. BMJ. 2020 Sep 2;370:m2930. doi: 10.1136/bmj.m2930. PMID: 32878745.
- Meissner HC. From Peyton Rous to the HPV Vaccine: A Journey of Discovery and Progress. Pediatrics. 2019 Nov 18;. doi: 10.1542/peds.2019-2345. [Epub ahead of print] PubMed PMID: 31740499.
- Naleway AL, Mittendorf KF, Irving SA, Henninger ML, Crane B, Smith N, Daley MF, Gee J. Primary Ovarian Insufficiency and Adolescent Vaccination. Pediatrics. 2018 Aug 21. pii: e20180943. doi: 10.1542/peds.2018-0943. [Epub ahead of print] PubMed PMID: 30131438.
- Phillips A, Hickie M, Totterdell J, Brotherton J, Dey A, Hill R, Snelling T, Macartney K. Adverse events following HPV vaccination: 11 years of surveillance in Australia. Vaccine. 2020 Aug 27;38(38):6038-6046. doi: 10.1016/j.vaccine.2020.06.039. Epub 2020 Jul 22. PMID: 32709432.
- Shimabukuro TT, Su JR, Marquez PL, Mba-Jonas A, Arana JE, Cano MV. Safety of the 9-Valent Human Papillomavirus Vaccine. Pediatrics. 2019 Nov 18;. doi: 10.1542/peds.2019-1791. [Epub ahead of print] PubMed PMID: 31740500.
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