How Government Data Is Being Misused to Question COVID-19 Vaccine Safety

Unverified reports linking the vaccine to deaths have been circulating on social and mainstream media for months

An image of  of COVID-19 vaccine collaged with torn graph paper. Photo Illustration: Lacey Browne/Consumer Reports, Getty Images

In April, an Ohio woman in her 50s died after suffering “blunt force injuries from a motorcycle accident,” according to a report of the incident. 

No other details about the crash or the woman were mentioned—save for one thing: About a week earlier, she had received her first dose of the Moderna coronavirus vaccine.

For that reason alone, details of the woman’s death were included in an obscure online government database known as VAERS (pronounced “vares”). It’s meant to be a place where anyone—healthcare providers, manufacturers, consumers—can report an adverse event after a vaccine is given. By design, reports are submitted without verification that the harm actually stemmed from the vaccine. 

But vaccine opponents and others have been using the database to stoke concerns about the safety of COVID-19 vaccines. In mid-September, for example, when speaking about the number of people who allegedly died from the COVID-19 vaccine, the Fox News host Tucker Carlson said “reports collected by the Biden administration itself indicate that number is actually in the thousands,” an apparent reference to the VAERS database. (A spokesperson for Carlson didn’t respond to a request for comment.)

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The Vaccine Adverse Event Reporting System is a database that has been administered by the Centers for Disease Control and Prevention and the Food and Drug Administration for more than three decades. It’s intended to be an early warning system for potential safety problems with vaccines licensed in the U.S. 

Manufacturers put vaccines through extensive clinical trials before they can be given to the public, and the FDA vets them, too. Once shots are administered, the government relies on systems like VAERS to capture potential rare adverse events that may occur, and then generate hypotheses about why that might be. The reports are published online for anyone to review. 

But there are caveats—many, many caveats. 

For one thing, VAERS data might be incomplete. Reports might lack significant details that make it difficult for researchers to assess what role, if any, a vaccine may have played. More critically, the existence of a report by itself doesn’t mean a vaccine caused the reported adverse event, a disclaimer reiterated numerous times across the government website that houses VAERS reports. 

Walter Orenstein, PhD, associate director of the Emory Vaccine Center and a professor of infectious diseases at the Emory University School of Medicine, says that VAERS functions as the first step in an extensive evaluation to determine whether a vaccine is causing adverse reactions or if the reports of harm are just coincidental. 

“VAERS is primarily what’s called a hypothesis generating system,” says Orenstein, who was director of the U.S. immunization program at the CDC from 1988 to 2004. “It gives you a signal that makes you suspicious, but then you need to do a more comprehensive scientific evaluation.” 

But vaccine opponents use the VAERS data—which may include cases such as someone injured in a motorcycle crash weeks after being vaccinated—to bolster their view about vaccines. And some news outlets have described academic research on the vaccine based on VAERS reports without noting the data’s many limitations. 

Regulators have long been aware that the data can be misinterpreted. But the government makes it public in the interest of transparency. And despite its shortcomings, the data has, in some cases, helped detect legitimate connections between a vaccine and adverse events. 

The Department of Health and Human Services, which oversees the CDC and FDA, didn’t provide answers in response to a request for comment.

“It’s frustrating to have to deal with these misinterpretations, especially when they interfere in such major ways with critical public health issues like the rollout of COVID-19 vaccines,” says Susan Ellenberg, PhD, a professor of biostatistics and epidemiology at the University of Pennsylvania’s Perelman School of Medicine. “But overall, I still think transparency is better.”

First Alert

All vaccines, including those against COVID-19, undergo rigorous clinical trials, in some cases involving tens of thousands of people. But those trials might not involve enough people with a particular risk factor, meaning certain issues might not be noticed by researchers at the earlier stages. Moreover, any vaccine might cause rare side effects that emerge later on. 

Launched in 1990, VAERS is used by the CDC and FDA to detect “concerning patterns or unusual and unexpected changes” that might indicate a safety problem once vaccines are on the market, according to a 2015 academic paper published by researchers at both agencies in the journal Vaccine.

“VAERS is important because it can capture events that were not routinely collected in active surveillance in clinical trials, more rare than would have been observed in trials because of limited sample sizes, or occur in populations not adequately studied in clinical trials,” says Steven J. Jacobsen, MD, interim executive director of the Marshfield Clinic Research Institute, a Wisconsin-based medical research institute, and former president of the American College of Epidemiology.

For example, government researchers investigated reports of myocarditis, or inflammation of the heart muscle, that were submitted to VAERS, and then alerted the public when they deemed that risk plausible. The CDC has said it’s continuing to monitor the development. 

VAERS reports on their own communicate only that some sort of adverse event, minor or major, happened after someone received a vaccine. Additional work and information are needed to establish whether the vaccine was the cause. 

Physicians, epidemiologists, and statisticians at the CDC and FDA assess the number of reports received, what sort of events are reported, and the number of doses distributed. Then they compare the rate an adverse event is reported in VAERS with the rate of the same adverse event with other vaccines. 

So while the reports alone generally can’t tie a vaccine to an adverse event, it can play an important role. 

“VAERS can often provide the earliest information on potential vaccine safety problems,” the 2015 vaccine paper by CDC and FDA researchers says. 

If it does detect potential safety issues, researchers at the CDC and FDA can then investigate further using other systems, such as the CDC’s Vaccine Safety Datalink, which receives more specific data from nine major healthcare organizations and can help measure “attributable risk,” says Emory’s Orenstein. 

Unverified and Misused

The website that hosts VAERS is plastered with disclaimers about the data’s limitations. “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,” one version of the warning reads. 

For example, “It seems quite plausible that a child could have an anaphylactic reaction on the way home from receiving a vaccine as a result of a bee sting,” Jacobsen says. “Because of these and other limitations, it makes it difficult to draw conclusions from studies of VAERS data.”

It’s frustrating to have to deal with these misinterpretations, especially when they interfere in such major ways with critical public health issues like the rollout of COVID-19 vaccines.

Susan Ellenberg, PhD

Professor of biostatistics and epidemiology, University of Pennsylvania's Perelman School of Medicine

And yet unsubstantiated claims are made anyway, and not just about the COVID-19 vaccine. The 2015 vaccine paper discusses articles circulated on the internet that attributed 100 deaths to the measles, mumps, and rubella (MMR) vaccine based on VAERS data.

But many of the deaths involved children with serious preexisting medical conditions or were otherwise unrelated to the vaccine, according to the paper.

The VAERS reports, additional health records, autopsy reports, and death certificates were reviewed by the CDC and FDA, the paper says, “and no concerning patterns emerged that would suggest a causal relationship with MMR vaccination and death.”

The System Can Work

Since its inception, VAERS has successfully identified a number of potential hazards that were found to be connected to a vaccine. 

One such case in the late 1990s involved the first vaccine to combat rotavirus, which can cause severe vomiting and diarrhea in infants. According to Orenstein, VAERS reports raised suspicions at the CDC and FDA of a potential link between the vaccine RotaShield to intussusception, a kind of bowel obstruction, within months.

Upon further investigation, Orenstein says, “we decided to stop the use of that vaccine.”

VAERS was also the mechanism that identified a rare event linked to the Johnson & Johnson vaccine for COVID-19. 

In April, the CDC and FDA announced they were reviewing six reports of a rare type of blood clotting out of the more than 6.8 million individuals who received the J&J shot in the U.S. The move led to a temporary pause in the distribution of the vaccine as regulators conducted a safety review.

That review ultimately led to the addition of a warning about blood clotting to the vaccine’s safety fact sheet.

The Value of Transparency

But if it’s impossible to draw conclusions from VAERS data without doing further inquiry, why publish it online at all? 

Researchers and experts who spoke with CR acknowledged that the data can be and is misused, but argued that total transparency is necessary to earn the public’s trust. 

“If [the data] are not publicly available, people will imagine that the government is hiding terrible stuff,” Ellenberg says. “They will not respond well to ‘just trust us, we are reviewing these data and will let you know if we find any problems.’”

Orenstein agrees. “The decision was that it would be better to get it out and then deal with misinterpretation than to hold on to it and then be accused of hiding information,” he says.

The CDC and FDA appreciate any reports received through VAERS, according to the 2015 vaccine paper, “even if the reporter is not sure if a vaccine caused the event.”

“VAERS accepts all reports without rendering judgment on clinical importance or whether vaccine(s) might have caused the adverse event,” the paper says. 

But how well the government combats the misinterpretation of VAERS data is an unanswered question. 

Ellenberg points out the CDC and FDA already publish “a lot of explanatory material” on VAERS for people to examine before accessing the data. But, she says, “nothing will distract those who believe they or their child were damaged by a vaccine, and it’s that small group that is vocal and gets public attention.” 

Head shot of Ryan Felton, a CR author of investigative reports and special projects

Ryan Felton

I'm an investigative journalist with an appetite to cover anything and everything. My job and goal is to dig into complicated issues that affect people's health, safety, and bottom line. I've covered everything from dangerous tires to subprime lending to corporate malfeasance. Got a tip? Drop me an email (, or follow me on Twitter ( @ryanfelton) for my contact info on Signal.