A source familiar with the event, who spoke on the condition of anonymity, said in an interview on Tuesday that the afflicted volunteer had experienced symptoms consistent with a condition called transverse myelitis, or inflammation of the spinal cord.
In a statement to reporters on Wednesday, an AstraZeneca spokesperson, Michele Meixell, said that the individual did not have a confirmed case of transverse myelitis. She said that the company’s chief executive, Pascal Soriot, had stated in a phone call reported by STAT “that there is no final diagnosis and that there will not be one until more tests are carried out. Those tests will be delivered to an independent safety committee that will review the event and establish a final diagnosis.”
The company did not respond to a request for clarification about whether transverse myelitis was suspected.
Transverse myelitis is relatively rare, sparking symptoms in roughly 1,400 people each year in the United States, according to the National Institutes of Health. The condition can result in pain, muscle weakness, paralysis or bladder problems. Its root cause is often mysterious, although doctors believe the syndrome generally results when inflammatory responses in the body go awry, sometimes as a reaction to an ongoing or past infection, said Dr. Felicia Chow, a neurologist at the University of California, San Francisco. “It’s not uncommon that we never figure out the cause,” she said.
There has been some past speculation that vaccines might be able to trigger transverse myelitis, she added. A handful of vaccines have previously been tied to a smattering of other autoimmune disorders, including Guillain-Barre syndrome, wherein the immune system attacks the nerves. Such complications, however, are rare.
Both transverse myelitis and Guillain-Barre syndrome have been pinpointed as possible complications of Covid-19.
Although vaccines are designed to be harmless to humans, they must still rouse the body’s defenses to marshal a protective immune response. But if the wrong subsets of cells or molecules are spurred into action, or if the body cannot rein in its own responses, this could set off a cascade that starts to damage healthy tissues, said Dr. Serena Spudich, a neurologist at Yale University.