The U.S. Food and Drug Administration (FDA) has released recommendations to monitor people who get vaccinated with Pfizer’s newly-approved coronavirus treatment for potential cases of Bell’s palsy after some subjects experienced the condition after getting the shots.

On Tuesday, the agency released a 54-page report that detailed how four cases of Bell’s palsy was observed on patients that were shot with Moderna’s coronavirus vaccine. The incidents were among 30,000 clinical trial volunteers. Three of the four received the actual treatment instead of a placebo shot.

Similarly, Pfizer’s trials observed four cases where patients developed the condition out of its nearly 43,000 participants. But in Pfizer’s case, all four of the victims received the coronavirus vaccine instead of the placebo.

The staff that reported Bell’s palsy cases said there was not enough evidence to correlate a link between the condition and Moderna’s coronavirus vaccine. However, the professionals urged close observation and monitoring of the patients that get the shot.

The FDA staff said that two of the three cases of Bell’s palsy with Moderna’s vaccine had been resolved while the other is still ongoing. The patients experienced the condition between 22 to 32 days after they were shot with the vaccine.

Health professionals explained Bell’s palsy as causing a person’s facial muscles to suddenly freeze or weaken and is usually temporary for many patients. Experts do not know the exact cause of the condition but theorize it comes from a viral infection or nerve inflammation or swelling.

The FDA staff said, “Current;y available information is insufficient to determine a causal relationship with the vaccine.”

On Thursday, the FDA’s Vaccines and Related Biological Products Advisory Committee is planned to meet to conduct its review of Moderna’s coronavirus vaccine. The committee was the one that endorsed Pfizer’s treatment last week before it was approved and began distribution.

A voting member of the FDA’s Vaccines and Related Biological Products Advisory Committee, Dr. Paul Offit, said monitoring the relationship of the vaccine and the condition was needed to ensure the safety of the patients. Last week, Offit voted for the approval of Pfizer’s coronavirus treatment. During an interview, he said, “I’m not dismissing that yet.”

When Merck, a pharmaceutical company, submitted data from its rotavirus vaccine trial that showed there were five cases of Kawasaki disease that developed from its tests. None of the conditions showed up in the placebo group. Merck officials said it was a significant finding and changed its label to show the information.

The FDA noted there was no certainty that the experimental drug was responsible for the development of the condition. The agency said, “because the number of cases was small and not more frequent than expected in the general population,” CNBC reported.

The agency’s guidance given to Moderna’s vaccine on Tuesday was similar to the one it gave Pfizer last week. Officials from the U.S. Centers for Disease Control and Prevention (CDC) said Pfizer’s treatment did not appear to result in the condition.

The director of the FDA’s Center for Biologics Evaluation and Research, Dr. Peter Marks, said on Monday that the agency said it would be able to swiftly access data on the condition after the vaccines have been injected into the patients.

Marks said, “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 close.”