Those opposed to vaccines (antivaxxers) are fond of quoting government figures to argue that there have been many adverse events due to COVID vaccines. They then proceed to state that because the government figures underreport these adverse events this means that the problem is much, much, worse. They also argue that there is a conspiracy to keep this information from the American public, and they demand that COVID vaccination should stop.
What are antivaxxers talking about? What are these government figures? Are they quoting them correctly? What do the numbers mean?
By the time vaccines are allowed to be used on the US population, they have gone through multiple clinical trials and other evaluations that have certified they are safe. But this vaccine safety is based on data gathered from at most a few tens of thousands of people. Therefore, it is understood that when vaccines are applied to a population of tens or hundreds of millions there may be some low frequency adverse events that may have not been detected in the clinical trials with a smaller group of people. To account for this, the government in 1990 created a federal database called VAERS (Vaccine Adverse Event Reporting System) that is meant to act as an early warning system to detect possible safety problems with vaccines.
However, VAERS is a passive reporting system. This means that anyone can file a VAERS report regardless of its nature, and that report is entered into the database and cannot be removed without the permission of the person who reported it. Although knowingly filing a false VAERS report is a violation of Federal law, if you are convinced that the adverse event you are describing, no matter how outlandish, is tied to a vaccine, it will be incorporated into the database.
For example, Dr. James Laidter mentioned in the neurodiversity weblog that back in 2005 he entered a VAERS report claiming that an influenza vaccine had turned him into the incredible Hulk, and the claim was accepted into the database. However, due to its unusual nature, a VAERS representative did contact him, and after an amicable discussion about the limitations of VAERS, the representative requested his permission to remove the claim to which he agreed. If he had not agreed to that, the claim would have remained in the database. Another example, Kevin Leitch writing for the Left Brain Right Brain science blog mentions that he submitted a VAERS report claiming that a vaccine had turned his baby girl into Wonder Woman, and he is not even a US resident!
However, even when considering reasonable adverse events, it must be understood that VAERS reports do not stablish that there is a link between the adverse events reported and vaccination. Each day thousands of people develop a health problem and/or die in the United States in a manner unrelated to vaccines. If any of these people received a vaccine around the time they developed the health problem or died, they could be reported to VAERS thus constituting a false positive.
The experts understand that the VAERS database has a high number of these false positives, and they use the database as a very preliminary step to perform more research, gather more data, and establish for sure whether a given event being reported is a real adverse event due to vaccines or not. These experts know that quoting numbers directly from the VAERS system is meaningless insofar as learning anything about the safety of vaccines is concerned. But this is exactly what antivaxxers do! And while some antivaxxers may be ignorant about the nature of VAERS, many of the leading antivaxxer influencers know the shortcomings of VAERS and nevertheless choose to continue reporting or quoting the raw numbers to advance their platforms and promote their agendas.
Antivaxxers are also prone to saying that VAERS vastly underestimates the number of vaccine adverse events by as much as 99%, so in some of their alarmist literature they suggest that VAERS numbers should be increased by large multiples. However, although reporting to VAERS of non-serious adverse events such as soreness at the injection site is indeed very low, estimates of the sensitivity of VAERS to serious adverse events, while variable, is much higher than antivaxxers would like us to think. For example, for anaphylaxis due to seven different vaccines, estimates of VAERS reporting sensitivity ranged from 13% to 76%, while for Guillain-Barre Syndrome after three different vaccines the sensitivity ranged from 12% to 64%.
Despite its shortcomings, the VAERS system has been useful for detecting rare side effects of the COVID-19 vaccines. For example, an elevated risk of myocarditis and pericarditis has been detected in males 12-29 years of age who have received mostly two doses of the Moderna or Pfizer mRNA COVID-19 vaccines. This is a treatable disease that involves inflammation of the heart or its surrounding membranes. The CDC convened a meeting of experts (the Advisory Committee on Immunization Practices: ACIP) to analyze these cases. The analysis involved weighing any harm caused by the vaccine against its benefits. The committee concluded that the benefits of vaccination outweighed the risks. However, now that we know that this age group is at an elevated risk of myocarditis/pericarditis, vaccine providers and healthcare professionals have been alerted to this side effect and its treatment.
This is the way VAERS and science are supposed to work. Rare adverse events of a vaccine are detected, and the risk/benefit is determined after a thorough evaluation of the data available. Then a rational course of action is pursued to achieve the greatest benefit with the least harm. The irresponsible use of VAERS by antivaxxers’s to concoct alarmist articles and memes promotes vaccine hesitancy which in turn prolongs the pandemic, leading to more hospitalizations and deaths and may give rise to new variants of the virus that are more resistant to the vaccine.
Photo of the Pfizer-BioNTech vaccine from Max Pixel is in the public domain.