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Home » Anti-vaxxers misuse VAERS against COVID-19 vaccines – bad science

Anti-vaxxers misuse VAERS against COVID-19 vaccines – bad science

Recently, a poorly written pre-print article uses VAERS “data” to show that the COVID-19 vaccines cause myocarditis in children 12-17 years old. Although we do have some data that the COVID-19 mRNA vaccines may be linked to myocarditis in some age groups.

I, and many others, have frequently criticized the use of VAERS, and I will do it again in this article, so just hang on. It cannot be used for anything by gross observations, and it certainly cannot be used as the basis for an article that condemns a vaccine.

So, let’s once again go down the rabbit hole of misusing VAERS to evaluate the safety of COVID-19 vaccines.

What is VAERS?

The Vaccine Adverse Event Reporting System (VAERS) is one of the systems employed by the US Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) to monitor vaccine safety. VAERS is a post-marketing surveillance program, collecting information about adverse events (including death) that occur after the administration of vaccines to ascertain whether the risk-benefit ratio is high enough to justify the continued use of any particular vaccine.

VAERS, the Vaccine Safety Datalink (VSD), and the Clinical Immunization Safety Assessment Network (CISA) are the major tools used by the CDC and FDA to monitor vaccine safety. These are powerful tools that actually provide full information about each patient so that correlation and causation may be determined through powerful case-control or cohort analyses of the data.

There are no analyses that can establish any type of causality between the vaccination event and the claimed adverse event that is reported to the VAERS database. Frankly, it can be gamed by those with nefarious intentions, which can limit the value of the VAERS data.

To be honest, VAERS is a feel-good system for those who think that there’s a link between vaccines and something terrible, but without an active investigation, the data is just above the level of totally meaningless. Most epidemiologists know it is valueless as a database to determine correlation and/or causation. Even the VAERS system itself says that the data cannot be used to ascertain the difference between coincidence and true causality.

According to the CDC:

Established in 1990, the Vaccine Adverse Event Reporting System (VAERS) is a national early warning system to detect possible safety problems in U.S.-licensed vaccines. VAERS is co-managed by the Centers for Disease Control and Prevention (CDC) and the U.S. Food and Drug Administration (FDA). VAERS accepts and analyzes reports of adverse events (possible side effects) after a person has received a vaccination. Anyone can report an adverse event to VAERS. Healthcare professionals are required to report certain adverse events and vaccine manufacturers are required to report all adverse events that come to their attention.

VAERS is a passive reporting system, meaning it relies on individuals to send in reports of their experiences to CDC and FDA. VAERS is not designed to determine if a vaccine caused a health problem, but is especially useful for detecting unusual or unexpected patterns of adverse event reporting that might indicate a possible safety problem with a vaccine. This way, VAERS can provide CDC and FDA with valuable information that additional work and evaluation is necessary to further assess a possible safety concern.

The VAERS website adds the following disclaimer:

VAERS accepts reports of adverse events and reactions that occur following vaccination. Healthcare providers, vaccine manufacturers, and the public can submit reports to the system. 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.

The strengths of VAERS are that it is national in scope and can quickly provide an early warning of a safety problem with a vaccine. As part of CDC and FDA’s multi-system approach to post-licensure vaccine safety monitoring, VAERS is designed to rapidly detect unusual or unexpected patterns of adverse events, also known as “safety signals.” If a safety signal is found in VAERS, further studies can be done in safety systems such as the CDC’s Vaccine Safety Datalink (VSD) or the Clinical Immunization Safety Assessment (CISA) project. These systems do not have the same scientific limitations as VAERS, and can better assess health risks and possible connections between adverse events and a vaccine.

In essence, VAERS is nothing more than anecdotes that have limited value. But, it is not valueless. It can be used as a safety signal – if researchers observe a large number of reports for something, say myocarditis, then the scientific method should be employed to determine if the signal is something more than coincidence.

Here’s how real researchers use VAERS:

  1. Observation. Note the number of reports that myocarditis is observed after COVID-19 vaccination.
  2. Hypothesis. Ask the question, “is the COVID-19 vaccine linked to myocarditis?”
  3. Test the hypothesis. Researchers could use the VSD, which contains full medical histories of patients who received and did not receive the vaccine. In otherwords, it’s real-world data that includes a “control group.” So, researchers could search for all cases of myocarditis in the database, and see who was vaccinated or not. Or they could look at all patients in the database, split them into vaccinated and unvaccinated and see if there’s a difference in myocarditis risk.
  4. Publish the results in a peer-reviewed journal.

In fact, this has been done for myocarditis and COVID-19 vaccines, using VAERS data for observational data, but then using VSD for a powerful, large epidemiological study.

blue and silver stetoscope
Photo by Pixabay on

What is myocarditis?

Before we start, we need to describe myocarditis, also known as inflammatory cardiomyopathy. It is a very rare inflammation of the heart muscle. Symptoms may include shortness of breath, chest pain, decreased ability to exercise, and an irregular heartbeat. The duration of the condition can vary from hours to months. Complications of myocarditis may include heart failure due to dilated cardiomyopathy or cardiac arrest.

Most of the time, myocarditis is caused by an infection that reaches the heart. 

Many of the cases are caused by a virus that reaches the heart. These can include influenza virus (flu), coxsackieviruscytomegalovirus, adenovirus, and others. The condition may also be caused by bacterial infections such as Lyme disease, streptococcus, mycoplasma, and chlamydia.

When the infection reaches the heart, the immune cells that fight the infection enter the heart. These immune cells produce biochemicals that can damage the heart muscle. Consequently, the heart itself can become thick, swollen, and weak.

As you can see, some sort of infectious pathogens, such as viruses and bacteria, are almost always implicated in the etiology of myocarditis. And remember, all of the COVID-19 vaccines do not contain the live SARS-CoV-2 virus, they only have a piece of code for the spike protein of the virus.

In the vast majority of cases, the effects are temporary, and the condition resolves itself.

government health hospital medicine
Photo by Mufid Majnun on

The VAERS and COVID-19 vaccines preprint

The paper, by Tracy Beth Høeg and others, was posted to the preprint server, medRXiv. Let me be clear about preprints right up front – they have been valuable during the COVID-19 pandemic to get out information. However, they are not peer-reviewed, and it’s difficult to determine what percentage of articles on the server ever get published. Peer-review of these articles now takes place on social media and blogs, but people, especially anti-vaxxers, are cherry-picking bad research to criticize the vaccines.

Furthermore, one of Høeg’s co-authors, Josh Stevenson, is a leader with the COVID-denier group “Rational Ground” which appears to be also anti-vaccine. This was not mentioned in the paper, a glaring conflict of interest that was ignored.

Høeg, who appears to do research in sports medicine, and one of the other co-authors, Allison Krug, have backgrounds in epidemiology. They should know better than to use VAERS as a database. This is disappointing.

Høeg et al. is being used by those with an anti-vaccine agenda as “evidence” that vaccinating 12-17-year-olds against COVID-19 is actually more dangerous than COVID-19 itself. They dumpster-dived into VAERS to assert that the risk of myocarditis in this age group from COVID-19 vaccines is higher than from the disease itself.

Several other people that are metric tonnes smarter than this old feathered dinosaur, such as Dr. David Gorski and Dr. Dan Freedman, have written long, careful analyses of this VAERS dumpster-diving. I’m just going to list out what I think are the most glaring issues with the preprint, but I would strongly suggest you read their articles for more detail.

  1. Methods part 1. Høeg et al. searched the Vaccine Adverse Event Reporting System (VAERS) data for females and males ages 12-17 in reports processed from 1/1/2021 through6/18/2021 with diagnoses of “myocarditis,” “pericarditis,” “myopericarditis” or “chest pain” in the symptom notes and required the term “troponin” in the laboratory data. This is not how VAERS should be used. One cannot ascertain whether those cases were properly diagnosed without reviewing the medical records. Furthermore, because myocarditis can occur for many more reasons than vaccines.
  2. Methods part 2. Many of the cases did not show whether one or two doses had been given. In real science, that data needed to be excluded, but the authors decided, in an attempt to prove their pre-ordaind conclusions, decided that they would be “assigned to dose 1 or dose 2 in the same proportion as the known doses: 15% occurred following dose 1 and 85% occurred following dose 2.” No, you don’t guess when doing epidemiological studies.
  3. Methods part 3.  The authors assume that hospitalization is the only bad outcome for children who develop COVID. Some of this age group have died. Some have developed long-term sequelae.
  4. Control 1. Their methods were extremely biased, so they were just searching for individuals that had myocarditis (irrespective of the fact that we don’t know if they were actually linked to the vaccine). The data wasn’t compared to a control group. That’s how real epidemiological studies are done.
  5. Control 2. I cannot emphasize this enough – they did not compare their results to the general population, an unvaccinated population, or anything else. Why? Because VAERS only includes complaints about a vaccine, it does not include the millions upon millions of people who got the vaccine and had nothing happen to them except to become immune to SARS-CoV-2. Again, VSD allows researchers to do this. If the authors really thought they were onto something, why didn’t they access the VSD database to develop a valid, and useful, article with strong epidemiology methods? They could have easily gotten access to the VSD database, there was no excuse for just using VAERS. This shows either incompetence, ignorance, or confirmation bias on their part.
  6. Risk benefit. The risk of myocarditis in the 12-17-year-olds with COVID-19 is about 450 per 1 million cases which is substantially higher than the 162 per million that the authors are claiming using VAERS data after COVID-19 vaccines. In fact, as I’ve written before, researchers examined the Vaccine Safety Datalink to examine the risk of myocarditis in this age group, and found about 6.3 additional cases per million after COVID-19 vaccination.

There’s so much more to write, but I don’t want this article to be a testament to your ability to read my long-winded diatribes. But this preprint deserves it.

conclusion word formed from lettered yellow tiles
Photo by Ann H on


Here we go with some really bad research from researchers (well, two of them Høeg and Krug) that violates every principle of good epidemiological research. Dumpster-diving into the VAERS database to try to “prove” that myocarditis is caused by COVID-19 vaccines is not the way to do it.

The authors should have tested their observations by using the Vaccine Safety Datalink, access to which only required a research protocol submitted to their Institutional Review Board, which would have given them much cleaner and more useful data. If they had done that, I would have been deeply troubled by the risk of vaccines.

I don’t know why the authors didn’t go to the VSD. Did they not know it existed? Did they not want to do real research? Were they worried that the VSD would nullify their hypothesis? Were they just lazy? I don’t know, and I don’t care. Now, this article has become another example of terrible research being held up by anti-vaxxers.

Of course, other researchers, have used VSD to look at the risk of myocarditis after vaccination and found nothing like the Høeg numbers. That’s because good research is equal to good science which is equal to good conclusions.

Right now, the best evidence we’ve got shows that post COVID-19 vaccination might be linked to a slightly increased risk of myocarditis, but it’s still far below the risk of myocarditis from COVID-19 itself.


  • Klein NP, Lewis N, Goddard K, Fireman B, Zerbo O, Hanson KE, Donahue JG, Kharbanda EO, Naleway A, Nelson JC, Xu S, Yih WK, Glanz JM, Williams JTB, Hambidge SJ, Lewin BJ, Shimabukuro TT, DeStefano F, Weintraub ES. Surveillance for Adverse Events After COVID-19 mRNA Vaccination. JAMA. 2021 Sep 3. doi: 10.1001/jama.2021.15072. Epub ahead of print. PMID: 34477808.
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