FDA Plans to Warn J&J Covid-19 Vaccine Raises Risk of Rare Neurological Condition

Guillain-Barré syndrome is a rare neurological disorder in which the immune system attacks nerves, causing temporary but potentially severe paralysis. The risk is a known one with vaccines, including some influenza vaccines and a leading shot to prevent shingles.

J&J didn’t immediately provide a comment.

The warning would be the latest for a vaccine that federal health officials had cautioned raises the risk of a rare blood-clotting condition.

The risk of Guillain-Barré, however, is very low, the person said, with a rate of about three to five cases per million recipients. The risk in the general population is about 1 in one million.

Some 12.7 million people in the U.S. have gotten the one-dose J&J vaccine, according to the Centers for Disease Control and Prevention.

The Johnson & Johnson vaccine uses a harmless type of common-cold virus called an adenovirus. It is engineered to carry a piece of genetic code instructing the body’s cells to make something resembling the spike protein that juts from the surface of the coronavirus.

Production of the spikelike protein, in turn, triggers an immune response that can protect a vaccinated person from Covid-19.

Another Covid-19 vaccine, from

AstraZeneca

PLC, which isn’t authorized in the U.S. but used in the U.K. and other countries, uses a technology similar to J&J’s. AstraZeneca’s shot also is linked to an increased risk of Guillain-Barré, federal health officials said.

AstraZeneca didn’t immediately respond to a request for comment.

The U.S. authorized the Johnson & Johnson vaccine in late February. Its rollout has struggled after regulators ordered a temporary pause in its administration as investigators studied the rate of the rare clotting disorder among vaccinated people.

The FDA recommends use of the vaccine, saying the benefits outweigh the risks. The agency, however, attached a warning to the vaccine’s label about the risk of the disorder and made recommendations for treatment.

The vaccine requires only one dose and doesn’t need to be stored at ultralow temperatures like messenger RNA vaccines do, which makes it a more straightforward and easier shot for vaccinating people, especially in places for which the freezer conditions and patient follow-up for a second shot would be more difficult to achieve.

Write to Thomas M. Burton at tom.burton@wsj.com and Felicia Schwartz at felicia.schwartz@wsj.com