The Johnson & Johnson vaccine will soon have a new warning from the Food and Drug Administration after the shot was linked to a rare but serious side effect in a handful of patients, it was revealed Monday. The side effect, Guillain-Barré syndrome — a condition that occurs when the immune system attacks the body’s nerves — has been detected in about 100 people after 12.8 million jabs of the single-dose shot were administered, the Centers for Disease Control and Prevention told the Washington Post. The outlet, citing four individuals familiar with the situation, reported the FDA is preparing to announce the warning after the adverse reactions came to light. Instances of Guillain-Barré syndrome post-vaccination were predominantly seen in men age 50 and older and reported about two weeks after inoculation, the outlet said. Current data doesn’t suggest a similar risk with the mRNA vaccines from Pfizer and Moderna. About 60 to 120 cases of the condition are seen each week and it typically occurs following a viral infection, but the exact causes are unknown. While most people fully recover, some people have permanent nerve damage and the condition is particularly risky for those over 50, the CDC said. The side effect is the latest setback for the Johnson & Johnson vaccine, which has been plagued by a series of hurdles since it was approved for emergency use in late February. Use of the vaccine, which has been heralded for its single-shot ease and its ability to inoculate hard-to-reach populations, was paused after it was linked to severe blood clots among younger patients.