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Bell's Palsy in COVID-19 Vaccine Trials: Why You Shouldn't Worry

bell's palsy

 Verywell / JR Bee

Key Takeaways

  • 7 cases of Bell's palsy, a type of facial paralysis, were reported by Pfizer and Moderna COVID-19 vaccine trial participants.
  • The frequency of these cases is no greater than the frequency of Bell's palsy in the general population.
  • Symptoms of Bell's palsy almost always resolve themselves.

Reports released from Pfizer and Moderna show that seven COVID-19 vaccine trial participants experienced a type of facial paralysis, called Bell's palsy, in the weeks after vaccination. This rare side effect, in tandem with three reports of severe allergic reactions, has raised some alarm about the safety of the new vaccines.

An analysis of the number of Bell's palsy incidents reported so far, however, shows the rate is no higher than the number of people who experience Bell's palsy in the general population. 

What Is Bell's Palsy?

Bell's palsy is a nerve condition that causes partial or complete weakness of one side of the face. The symptoms—like a sagging eyebrow or drooping mouth—come on suddenly, and typically resolve over the course of a few weeks or months. While it's usually difficult to pinpoint a cause, viral infections can trigger Bell's palsy.

 According to the National Institutes of Health, Bell's palsy affects about 40,000 people in the United States every year, which is 0.01% of Americans. 

In the Pfizer-BioNTech clinical trial, which included 44,000 participants, 4 people reported experiencing Bell's palsy, which is 0.0091% of participants. The incidents were reported 3,9, 37, and 48 days after vaccination. No cases of Bell's palsy were reported in the placebo group.

In the Moderna clinical trial, which included 30,400 participants, 3 people reported experiencing Bell's palsy, which is 0.099% of participants. One person was in the placebo group. Among the three not in the placebo group, the Bell's palsy incidents were reported 32, 28, and 22 days after vaccination. 

While the U.S. Food and Drug Administration (FDA) briefing documents provided by Pfizer and Moderna indicate these rates of Bell's palsy "do not represent a frequency above that expected in the general population," the FDA recommends surveillance for Bell's palsy as the vaccines are distributed among the general population.  

For anyone who does experience Bell's palsy, the condition is treatable. Oral steroids, especially if administered within 72 hours of symptom onset, are highly effective at restoring nerve function. 

What This Means For You

The few reported incidents of Bell's palsy in COVID-19 vaccine clinical trials should not deter you from getting the vaccine if you are eligible. So far, the number of incidents is no greater than the amount of people who experience Bell's palsy in the general population, suggesting this may be a coincidence. 

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

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Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Institutes of Health. Bell’s Palsy Fact Sheet. Updated October 2, 2020.

  2. U.S. Food and Drug Administration. Vaccines and Related Biological Products Advisory Committee meeting December 10, 2020. FDA briefing document: Pfizer-BioNTech COVID-19 vaccine. December 10, 2020.

  3. U.S. Food and Drug Administration. Vaccines and Related Biological Products Advisory Committee meeting December 17, 2020. FDA briefing document Moderna COVID-19 vaccine. December 17, 2020.