June 24 (UPI) -- People with COVID-19 are nearly seven times more likely to develop Bell's palsy, or facial muscle paralysis, than those vaccinated against the virus, a study published Thursday by JAMA Otolaryngology-Head & Neck Surgery found.
While early reports suggested the condition could be a side effect of vaccination against the coronavirus, researchers said the study does not indicate the vaccine is at fault.
The complication, though, is uncommon, affecting well under one-tenth of 1% of people infected with the coronavirus, the data showed.
In addition, many of those who develop Bell's palsy following infection have a history of the disorder, suggesting the virus causes a recurrence of its symptoms.
"In the early period of the COVID-19 vaccine availability, there were several media reports of Bell's palsy associated with vaccination [and] such concerns could erode vaccine confidence and exacerbate public hesitancy," study co-author Dr. Akina Tamaki told UPI in an email.
However, "our data suggests that rates of Bell's palsy are higher in patients who are positive for COVID-19 and this incidence exceeds the reported incidence ... with the COVID-19 vaccine," said Tamaki, assistant professor of otolaryngology at Case Western Reserve University in Cleveland.
COVID-19 is known to cause high levels of inflammation in multiple organs, including the lungs, heart and brain, particularly in those with severe illness, research suggests.
Among the complications associated with this widespread inflammation are neurological disorders, including Bell's palsy, an episode of facial muscle weakness or paralysis that begins suddenly and is caused by damage to the facial nerve.
Because the currently available COVID-19 vaccines are designed to trigger an immune response similar to that brought on by coronavirus infection -- to prepare the immune system to respond to the real virus -- there have been concerns that they may cause similar complications.
Phase 3 clinical trials of the Pfizer-BioNTech and Moderna COVID-19 vaccines found that roughly 19 of every 100,000 people inoculated developed Bell's palsy, though it could not be confirmed that the shots caused the complication, according to Tamaki and her colleagues.
For this study, the researchers analyzed data on more than 348,000 patients diagnosed with COVID-19 and about 64,000 who had been vaccinated against the virus.
Of the infected, patients, 284, or 0.08%, were diagnosed with Bell's palsy within eight weeks of testing positive for the virus, the data showed.
Fifty-four percent of these patients had no history of the facial muscle disorder, while 46% had been diagnosed with it in the past.
There were no cases of Bell's palsy among the vaccinated participants, none of whom had a prior history of COVID-19, they said.