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Ciara O'Rourke
By Ciara O'Rourke December 15, 2022

No, Pfizer didn’t say stiff-person syndrome is an adverse effect of COVID-19 vaccine

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  • Medical experts say there’s no evidence that COVID-19 vaccines cause stiff-person syndrome. Scientists still don’t understand the neurological disorder’s cause. 
  • The disorder appears on a list of adverse event reports in a 2021 document from Pfizer, but that isn’t the company conceding that the vaccine causes the disorder. Such reports can be unverified and are not evidence of a causal relationship between the COVID-19 vaccine and the health problems.

Singer Celine Dion recently announced that she needed to reschedule her upcoming tour because she was struggling with a stiff-person syndrome diagnosis. 

The rare, progressive neurological disorder that affects one or two people per million can cause stiff muscles, spasms and more, and scientists don’t yet understand the disease’s cause.

But some social media users suggested that a cause has been identified: COVID-19 vaccines. 

"You will never guess what’s in Pf**er’s own documents," reads text above a screenshot of a document that lists numerous illnesses alphabetically. "Stiff-person syndrome" is circled. 

An Instagram account sharing the image tagged Dion in the post

This post was flagged as part of Facebook’s efforts to combat false news and misinformation on its News Feed. (Read more about our partnership with Meta, which owns Facebook and Instagram.)

The National Institute of Neurological Disorders and Stroke says on its website that research suggests stiff-person syndrome is "the result of an autoimmune response gone awry in the brain and spinal cord." The disorder was first described in 1956, when it was named stiff man syndrome. 

Johns Hopkins Medicine has a "Stiff-Person Syndrome Center" at which it follows more people with this condition than anywhere else in the world, according to its site. "This means we have access to the latest knowledge in stiff person syndrome and can apply that insight to each patient," the site says. 

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Dr. Scott Newsome, the center’s director, told Reuters, "There is no data or evidence to suggest that the COVID-19 vaccine causes stiff-person syndrome." 

Pfizer also told PolitiFact that it has identified no causal link between its COVID-19 vaccine and stiff-person syndrome. The screenshot in the Instagram post is part of a November 2021 document from Pfizer about analyzing adverse event reports through February 2021. 

"Stiff-person syndrome" appears in a list titled "Appendix 1. List of adverse events of special interest." 

It’s among nine pages of illnesses that are considered adverse events of special interest, which regulators want the company to look out for. But they aren’t necessarily adverse events that have been linked to COVID-19 vaccines. 

Pfizer also notes that reports of such adverse events may lack causal relationships. Such reports in the company’s safety database include cases reported by health authorities, published in medical literature and cases reported from clinical studies — all "regardless of causality assessment." 

It includes voluntary reports through national reporting systems like the Vaccine Adverse Event Reporting System, a database that helps researchers collect data on vaccine aftereffects and has also fueled misinformation about COVID-19 vaccines. Anyone can submit a report to the reporting system; they’re not verified, and the Centers for Disease Control and Prevention warns that they’re not enough to determine whether a vaccine causes a particular adverse event.

Dion has not said or suggested that a COVID-19 vaccine is behind her illness or her changing tour schedule. And Pfizer hasn’t said that its COVID-19 vaccine causes stiff-person syndrome. 

We rate claims that the company confirmed it does False.

RELATED: Baseless claims about COVID-19 vaccine paralysis and Celine Dion spread online

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No, Pfizer didn’t say stiff-person syndrome is an adverse effect of COVID-19 vaccine

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