The U.S. Food and Drug Administration is expected to announce a Johnson & Johnson vaccine warning after over 100 preliminary reports of a rare autoimmune disease have been detected, the Washington Post reports. 

The Guillain-Barré syndrome reports were detected mostly in men over the age of 50, according to the Post, of the 12.8 million people who had the vaccine in the U.S. The neurological condition sees the body’s immune system attack a protective coating on nerve fibers after a bacterial or viral infection in many cases.

The condition has previously been linked with the 2009 H1N1 flu pandemic and a vaccine for the 1976 Swine Flu outbreak. Roughly 3,000 to 6,000 people develop GBS each year on a national level. 

An official told the Post that reports may be “rare,” but they “do likely indicate a small possible risk of this side effect following this vaccine.” 

The J&J vaccine has already been linked to rare blod-clotting condition, which has previously slowed down the shot’s production. But in April, regulators decided to keep the vaccine going as the benefits outweighed the risks.

Those in Europe, too, are asking for a similar warning on the AstraZeneca’s COVID-19 vaccine, which Reuters reports is based on technology similar to J&J.