Trish Greenhalgh, professor of primary care health sciences at the University of Oxford, told The BMJ that although all preprints were suspect before they were peer reviewed, some were more suspect than others.
She said, “The VAERS database is a passive monitoring system maintained by the US Food and Drug Administration and Centers for Disease Control and Prevention that invites the public to report any perceived or suspected side effects following vaccination, so that potential signals of harm may be investigated further. Crucially, all such reports must be validated by other active monitoring systems, as VAERS entries are very prone to reporting and recall bias.
“Indeed, the CDC explicitly states that VAERS cannot be used in isolation to infer the existence, frequency, or rates of vaccine complications.”
Greenhalgh said that although the FDA and CDC used VAERS data to generate hypothesis driven questions about effects of covid vaccines in teenagers, the agencies then investigated before concluding that these vaccines were safe. “VAERS data dredging, as it is known, has been used by antivaccine groups in the past to produce alarmist estimates of harms from vaccines,” she said.