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Home » Bell’s palsy and COVID-19 mRNA vaccines – let’s temper the concerns

Bell’s palsy and COVID-19 mRNA vaccines – let’s temper the concerns

A new issue has arisen with the Pfizer and Moderna COVID-19 mRNA vaccines – Bell’s palsy, a type of facial paralysis. The FDA has issued a “staff report” on Tuesday, 15 December 2020, that recommends monitoring people who receive those vaccines be monitored for the condition.

As I wrote earlier about the Moderna COVID-19 vaccine facts, there were a few reports of the condition after vaccination. However, we need to examine the situation carefully, so that we all have accurate information about the seriousness (or lack thereof) of this risk.

So, let’s dive into this.

By James Heilman, MD – Own work, CC BY-SA 3.0.

What is Bell’s palsy?

Bell’s palsy is the most common cause of facial paralysis, which probably sounds troubling to many of the readers. The condition usually affects just one side of the face.

Symptoms appear suddenly and are at their worst about 48 hours after they start. They can range from mild to severe and include:

  • Twitching
  • Weakness
  • Paralysis
  • Drooping eyelid or corner of the mouth
  • Drooling
  • Dry eye or mouth
  • Excessive tearing in the eye
  • Impaired ability to taste

Scientists have hypothesized that viral infection causes the facial nerve to swell or inflame. There is a higher risk of Bell’s palsy in pregnant or diabetic individuals along with those who have contracted the flu or a cold. 

Facial nerves that cause Bell’s palsy.

About 75% of patients improve without treatment. Symptoms resolve quickly, usually within two weeks, and full recovery occurs within three to six months. Bell’s palsy may seem like a frightening condition, but it is very mild and is almost always temporary.

Severe or permanent conditions are extremely rare.

And what about the new COVID-19 vaccines?

Let’s get right to the point – the FDA does not consider Bell’s palsy to be a side effect of either the Moderna or Pfizer vaccines. However, because each vaccine’s phase 3 clinical trials showed a tiny number of incidents of the condition, the FDA, because it’s a cautious agency, has decided to monitor the situation.

During the Moderna clinical trial, four out of approximately 30,000 people developed Bell’s palsy, three of those had received the vaccine. Similarly, four out of the 43,000 people in the Pfizer clinical trial contracted Bell’s palsy, all of whom received the vaccine.

The condition was noted between 22 and 32 days after receiving the vaccines. Two of the cases in the Moderna trial have already resolved.

As a comparison, the incidence of Bell’s palsy is about 2335 per 100,000 people per year, which is around 5X higher than what was observed in both arms of the Moderna and Pfizer clinical trials. In other words, the risk of Bell’s palsy is substantially lower in the vaccinated groups than in the general population.

The FDA staff stated that:

There were no other notable patterns or numerical imbalances between treatment groups for specific categories of adverse events, including other neurologic, neuro-inflammatory, and thrombotic events, that would suggest a causal relationship to the Moderna COVID-19 vaccine.

Peter Marks, MD, director of the FDA’s Center for Biologics Evaluation and Research, the division of the FDA that reviews vaccines, stated in an interview with JAMA:

Our working hypothesis is this just was an imbalance in background rates like we’ve seen in other trials, but we’ll make sure that we’re going to actually query for that just to bring that question to a close.

Bell's palsy


Bell’s palsy is a temporary condition that very rarely causes permanent facial paralysis. Although it was observed a total of eight times in over 73,000 participants in the clinical trials, it was difficult to find a direct cause between the vaccines and the condition.

In fact, Bell’s palsy is much more frequent in the general population than was observed during the clinical trials.

Of course, anti-vaccine activists have jumped on this as a major issue for the COVID-19 mRNA vaccines, despite the lack of evidence supporting a causal link. 

I don’t want to dismiss this as a myth pushed by those who are opposed to the vaccine since the FDA will monitor the situation, but it really does seem like a myth. Stay tuned, because if this becomes an issue, I will certainly write an update.


  • Holland NJ, Bernstein JM. Bell’s palsy. BMJ Clin Evid. 2014 Apr 9;2014:1204. PMID: 24717284; PMCID: PMC3980711.
  • Marson AG, Salinas R. Bell’s palsy. West J Med. 2000 Oct;173(4):266-8. doi: 10.1136/ewjm.173.4.266. PMID: 11017995; PMCID: PMC1071111.


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