Antivaccine activists use a government database on side effects to scare the public

Cars line up in a parking lot at NRG Park as people wait to receive a COVID-19 vaccine at a federally supported supersite at the Harris County facility, Wednesday, Feb. 24, 2021, in Houston. ( Mark Mulligan/Houston Chronicle via AP)

Meredith Wadman


On 5 May, Fox News host Tucker Carlson delivered a 10-minute monologue casting doubt on the safety of COVID-19 vaccines on his show, Tucker Carlson Tonight. He announced that almost 4000 people had died after getting COVID-19 vaccines, and added that those data “comes from VAERS,”—the Vaccine Adverse Event Reporting System, a U.S. government program that collects reports of side effects possibly caused by vaccines.

It was a misleading statement. The reporting of a death to VAERS indicates nothing about what caused it, and the Centers for Disease Control and Prevention’s (CDC’s) subsequent investigations have found no indication that deaths were caused by COVID-19 vaccines, save in a small subset with an extremely rare clotting disorder linked to one vaccine. But the TV segment pulled VAERS, a 31-year-old early warning system widely relied on by scientists, even deeper into the culture wars over vaccination. After the broadcast, a new phalanx of antivaccine activists began plumbing VAERS for data to scare the public about vaccination, says Angelo Carusone, president of Media Matters for America, a left-leaning nonprofit that is monitoring anti–COVID-19 vaccine activity on social media. “We have been tracking these attacks since February and this one resonated in a different way after Tucker hit it,” Carusone says.

It has been distressing to watch for researchers who use VAERS to detect real vaccine side effects—such as the very rare clotting disorder linked to the Johnson & Johnson (J&J) vaccine—and to rule out others, thus providing both safety and reassurance to the public. “I can’t believe people are using this database now to try to form this antivaccination argument,” says Eric Formeister, an ear surgeon at Johns Hopkins University.

Formeister and colleagues turned to VAERS, which is run by CDC and the Food and Drug Administration, after hearing anecdotal reports from patients of sudden hearing loss after COVID-19 vaccination. Their analysis of VAERS data concluded hearing loss was no more frequent, and possibly less frequent, among vaccine recipients than in the population as a whole, as they published in JAMA Otolaryngology last week. CDC is now using VAERS data to probe whether COVID-19 vaccines might rarely be causing heart inflammation in children; it has not yet reached a conclusion.

One of VAERS’s strengths—its openness—is also a potential weakness in the politicized COVID-19 era. Anyone who receives a vaccine authorized in the United States can report an adverse event to VAERS, as can doctors, family members, and others. That openness ensures VAERS receives plentiful reports—228,000 for COVID-19 vaccines alone since December 2020, more than four times the number received in all of last year for all vaccines.

Some worry this might make it easy to post false reports. But CDC removes data that are clearly fake, such as a recent report purportedly filed by Brazilian President Jair Bolsonaro about an adverse event in a beach volleyball superstar. And deliberate, false reporting to VAERS, which is a federal criminal offense, appears to be rare. “We don’t have evidence that there is widespread fraud or gaming of the system,” says Tom Shimabukuro, deputy director of CDC’s Immunization Safety Office, which oversees VAERS. “We have to balance keeping VAERS an open system and getting as much information as we can on vaccine safety against potential data quality problems.”

But even honest reports can be used to spook the public. The reports themselves are not vetted, and, as CDC states in a prominent disclaimer, they “may include incomplete, inaccurate, coincidental and unverified information.”

People may misinterpret VAERS, which is easily searchable, as a catalog of actual side effects, rather than possible or suspected ones. And it’s easy to pull data out of context. “For those who are out to scare, there’s a lot of material there,” says Heidi Larson, director of the Vaccine Confidence Project at the London School of Hygiene & Tropical Medicine.

Take Carlson’s fearful numbers. The Fox News host did not mention the reports are not vetted, nor that among the approximately 4000 deaths after COVID-19 vaccination reported to VAERS at the time of his broadcast, nearly 80% were in people 60 and older, whose mortality from all causes is substantially higher than in younger people. “A review of available clinical information, including death certificates, autopsy, and medical records has not established a causal link to COVID-19 vaccines,” as CDC puts it on its website.

To counter misinterpretation of its data, the VAERS website prominently notes the reports do not imply causality and that any event could have happened by coincidence. The number of deaths reported after a COVID-19 vaccination as of 24 May—4863—represents just 0.0017% of more than 285 million doses of vaccine given, the agency notes in a continuously updated statement.

But experts who track vaccine misinformation worry the imprimatur of VAERS gives misleading claims a sheen of credibility. “At the moment when we need to persuade people, there is something so incredibly compelling about a database that’s tracking what are designated as ‘adverse events,’” Carusone says. “That Tucker segment has created this catalyst for all sorts of analysis of the database,” including false claims that the vaccines kill babies and that CDC is hiding VAERS reports.

Carusone says the episode has gained particular traction on Spanish-language social media, where a translation was published 2 days later. There, false claims that COVID-19 vaccines cause infertility have also gained attention, although neither VAERS data nor Carlson’s newscast address that claim.

Despite the disinformation, the VAERS system is critical to keeping vaccines safe—and its history during COVID-19 shows it’s working, CDC officials say. VAERS data were crucial to CDC’s ability to quickly detect and guide providers and the public about rare allergic reactions caused by the Pfizer-BioNTech and Moderna vaccines and the even rarer problem with the J&J jab, says John Su, a physician who leads the VAERS team within CDC’s Immunization Safety Office. Keeping the system open to anyone who wants to report a suspected side effect or wants to consult the data is essential, he says.

But Larson says CDC and the public health community need to make a “serious investment right now” to more aggressively counter the misuse of VAERS data, for example by responding as quickly as possible to new myths that are gaining traction, and doing so in lay-friendly language and forums rather than arcane medical journals. “At least make sure you get the right information out there as soon as possible,” she says. “Watch how people misinterpret [VAERS data] … because it’s clearly being misinterpreted.”

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