• The FDA is expected to announce a new warning for the Johnson & Johnson Covid vaccine, saying the shot has been linked to a serious but rare autoimmune disorder, The Washington Post reported.
• About 100 preliminary reports of Guillain-Barre syndrome have been detected after 12.8 million doses of the J&J vaccine were administered, the CDC said.
• U.S. regulators are expected to emphasize that the J&J vaccine is safe and that its benefits clearly outweigh the potential risks, the Post reported, citing people familiar with the situation.

The Food and Drug Administration is expected to announce a new warning for Johnson & Johnson's Covid-19 vaccine, saying the shot has been linked to a serious, but rare, autoimmune disorder, The Washington Post reported Monday, citing four unnamed sources.

About 100 preliminary reports of Guillain-Barre syndrome have been detected after 12.8 million doses of the J&J vaccine were administered, the Centers for Disease Control and Prevention said in a statement to NBC News. Guillain-Barre is a rare neurological disorder in which the body's immune system mistakenly attacks part of the nervous system.

It is estimated to affect about one person in 100,000 each year, and most people eventually recover from the disorder, according to the National Institute of Neurological Disorders and Stroke.

The cases reported after receiving the J&J shot largely occurred about two weeks after vaccination and mostly in males, many aged 50 years and older, according to the CDC. Available data do not show a similar pattern with Pfizer's or Moderna's vaccine, the agency said.

U.S. regulators are expected to emphasize that the J&J vaccine is safe and that its benefits clearly outweigh the potential risks, the Post reported, citing people familiar with the situation.

The FDA did not immediately respond to CNBC's request for comment.

"Reports of GBS after receipt of the J&J/Janssen COVID-19 Vaccine in the Vaccine Adverse Event Reporting System (VAERS) are rare, but do likely indicate a small possible risk of this side effect following this vaccine," the CDC said in the statement to NBC News.

In a statement Monday, J&J said it has been in discussions with the FDA and other regulators about the disorder.

"The chance of having this occur is very low, and the rate of reported cases exceeds the background rate by a small degree," the company said. "We strongly support raising awareness of the signs and symptoms of rare events to ensure they can be quickly identified and effectively treated."

The anticipated new warning is just the latest setback for J&J, which has suffered from production problems of its vaccine as well as public concerns about a rare, potentially life-threatening, blood clotting disorder linked to its shots.

After its authorization in late February, the vaccine was touted as a blessing since it could be stored at refrigerator temperatures for months and takes just one dose — unlike Pfizer's and Moderna's, which require more complicated transportation methods and are two doses.

More than 12 million of the J&J shots have been administered in the U.S., according to data compiled by the CDC.

Read the full Post story here.