By Noah Rothstein

On July 12, the Food and Drug Administration (FDA) warned that Johnson & Johnson’s coronavirus vaccine could lead to an increased risk of a rare neurological condition known as Guillain–Barré syndrome, another setback for a vaccine largely sidelined in the United States. The first warning came after the vaccine was temporarily halted for 10 days after fears of blood clots back in April this year.

Although regulators have found that the chances of developing the condition are low, they appear to be three to five times higher among recipients of the Johnson & Johnson vaccine than among the general population in the United States, according to people familiar with the decision. The warning was attached to fact sheets about the vaccine for providers and patients.

Federal officials identified 100 suspected cases of Guillain-Barré among recipients of Johnson & Johnson’s one-dose shot through a federal monitoring system. Of those cases, 95% were considered severe and required hospitalization, the FDA said. The reports are preliminary.

Guillain-Barré syndrome occurs when the immune system damages nerve cells, causing muscle weakness and occasional paralysis, according to the FDA. Several thousand people, about 10 out of every million, develop the condition every year in the U.S. Most recover from even severe symptoms. It has also been reported in people with COVID-19.

In a statement, the agency said that while “the available evidence suggests an association” between the Johnson & Johnson vaccine and increased risk of Guillain–Barré syndrome, “it is insufficient to establish a causal relationship.”

The agency added that it “continues to find the known and potential benefits clearly outweigh the known and potential risks” of the vaccine.

About 12.8 million people, or about 8% of the fully vaccinated population in the United States, have received the Johnson & Johnson shot. By contrast, about 146 million have been fully vaccinated with Pfizer’s or Moderna’s vaccines, both of which require two doses.

The pace of vaccinations has slowed considerably as a new, more contagious variant called Delta is spreading quickly in under-vaccinated areas. Federal health officials worry that the J&J news could make people even more hesitant to accept not just the J&J vaccine, but those developed by Pfizer or Moderna, even though no evidence of increased risk of Guillain–Barré syndrome has been identified with them.

“What worries me most is that it reinforces the lack of confidence that people had,” said Dr. Steven Black, an emeritus professor of pediatrics at Cincinnati Children’s Hospital Medical Center and the co-director of the Global Vaccine Data Network, a consortium that researches the safety of vaccines.

The suspected cases were reported to the Vaccine Adverse Event Reporting System, a 30-year-old federal monitoring system. In a statement released on Monday, the Centers for Disease Control and Prevention (CDC) said the cases were mostly reported about two weeks after vaccination and mostly in men, many of them ages 50 years and older.

Johnson & Johnson said in a statement that “the risk of having this occur is very low, and the rate of reported cases exceeds the background rate by a small degree.”

Even though it requires only one dose and is easier to store than Pfizer’s and Moderna’s vaccines, J&J’s shot has played only a minor role in the U.S. inoculation campaign. That is partly because a plant in Baltimore that was supposed to supply most of the doses in the country was shut down for three months because of regulatory violations. The factory, operated by subcontractor Emergent BioSolutions, was forced to throw out the equivalent of 75 million doses because of suspected contamination, significantly delaying deliveries to the federal government.

Alex Gorsky, J&J’s chief executive, said last month that he was still hopeful that the vaccine, which has been used in 27 countries, would help contain the pandemic overseas. The company has promised up to 400 million doses to the African Union. Separately, Covax, the global vaccine-sharing program, is set to receive hundreds of millions of doses.

Studies show that the J&J shot protects people against more contagious coronavirus variants, including the Delta variant, and is highly effective at preventing severe COVID-19, hospitalizations, and death.

The Food and Drug Administration shares jurisdiction over vaccines with the CDC, but it is solely responsible for issuing product warnings. The Guillain-Barré cases will be discussed in an upcoming meeting of outside experts who advise the CDC, the agency said.

Federal regulators also attached warnings to the Pfizer and Moderna vaccines, but some government health officials described them as less serious. The CDC last month pointed to an increased risk of inflammation of the heart or the surrounding tissue, diseases known as myocarditis and pericarditis, particularly among adolescents and young adults who had received Pfizer or Moderna shots.

The CDC said that in most of the reported cases, symptoms promptly improved after rest or medication. By contrast, symptoms of Guillain-Barré typically require medical intervention, officials said.

The revised fact sheet for J&J’s shot states that recipients should immediately seek medical attention if they develop any of the following symptoms:

  • Weakness or tingling sensations, especially in the legs or arms, that worsens and spreads to other parts of the body.
  • Difficulty walking.
  • Difficulty with facial movements, including speaking, chewing, or swallowing.
  • Double vision or inability to move eyes.
  • Difficulty with bladder control or bowel function.

Currently, no COVID-19 vaccination is fully approved by the FDA. However, Pfizer, Moderna, and J&J were given emergency use authorization.