Publisher Health

In a meeting of its expert vaccine advisers on Thursday, the Centers for Disease Control and Prevention presented new details on concerning rates of a rare blood clotting condition linked to Johnson & Johnson’s Covid vaccine, including nine confirmed deaths.

The new data set the stage for the experts to consider recommending new restrictions on use of the vaccine. The panel, the Advisory Committee on Immunization Practices, could advise doing nothing, that the vaccine be restricted to only older people, or that it not be used at all in the United States. The panel could also recommend that Pfizer-BioNTech and Moderna’s vaccines should be preferred over Johnson & Johnson’s shot, except in cases where people cannot access a different brand or who want it despite the risk.

Earlier this week, the Food and Drug Administration issued updated guidance on the risks of the blood-clotting disorder, but said again that the benefits of the vaccine outweighed its risks.

C.D.C. officials went into detail on the clotting-related syndrome identified in 54 people in the United States who received the shot before the end of August. Overall, the rate of the condition was 3.8 cases per one million people given the vaccine. That is higher than the rate had been previously thought to be.

The risk for the condition, which is known as thrombosis with thrombocytopenia syndrome and can cause internal bleeding, was highest in women ages 30 to 49, showing up in about 1 in 100,000 recipients in that age group. The rate at which the condition would normally be expected in the general population is not known, said Dr. Isaac See, a C.D.C. official.

Of all Johnson & Johnson vaccine recipients diagnosed with the condition, 36 were admitted to an intensive care unit and the longest hospital stay was 132 days. Eight of them died. Since September, a ninth person has died.

“We’ve been struck from reviewing these cases by how rapidly the status deteriorates and results in death,” Dr. See said.

The people who died ranged in age from 28 to 62. Seven were women, and all were white. Obesity was the most common underlying medical condition. Two of the people who died did not have known medical problems, Dr. See said.

Dr. See said additional cases had been identified since earlier C.D.C. meetings because of lags in reporting and delays in identifying and confirming illnesses related to the vaccine.

An increased risk for the condition has been linked to the Johnson & Johnson vaccine and the shot from AstraZeneca, which is not authorized in the United States. It has not been linked to the vaccines from Moderna or Pfizer.

On Thursday, C.D.C. officials also reported on side effects among children aged 5 to 11 who have received the Pfizer vaccine in the last several weeks. With 7.1 million doses administered, the C.D.C. confirmed eight cases of myocarditis, or swelling of the heart muscle, and has an additional case under review.

It was previously reported that males between 16 and 29 years had a heightened risk of developing myocarditis. Nearly 11 out of every 100,000 of them developed the condition a few days after being fully vaccinated. On balance, it was estimated that for boys 12 to 17, the shots would cause an estimated 70 myocarditis cases but prevent 5,700 infections, 215 hospitalizations and two deaths, the C.D.C. said. But most recovered within a short period of time.

Among the six cases in younger children with known outcomes, five recovered from the symptoms. The eight confirmed cases were evenly split between males and females.

The other serious side effects documented were fevers, vomiting and chest pain reported among fewer than 60 children combined. Two children, ages 5 and 6, both with cerebral palsy and additional medical conditions, died.

About 16 million people in the United States have received a single shot of the Johnson & Johnson vaccine as their primary immunization, compared to 73 million fully immunized with Moderna’s vaccine and 113 million with Pfizer’s. Among the people in the United States who have received a booster shot, just 1.5 percent have gotten the one from Johnson & Johnson.

Jake Sargent, a spokesman for Johnson & Johnson, said the company shares with regulators reports of side effects in people who have received the vaccine and “strongly support raising awareness of the signs and symptoms of this rare event.”

On Tuesday, the Food and Drug Administration announced that it added a warning to the vaccine’s fact sheets for patients and providers, saying the shot should not be given to anyone who has had a clotting problem after a first dose. The agency said that it “continues to find” that the benefits of the vaccine outweigh its risks.

In April, soon after Johnson & Johnson’s vaccine started being administered in the United States, federal officials briefly halted use of the shot because of concerns about the risk of blood clots. Other countries also moved to pause use of the shot, and some suggested that women in the at-risk age groups be advised to seek other vaccines.

The Johnson & Johnson shot has largely fallen out of favor in the United States, despite early hopes that its one-and-done format would be easy to deploy in more isolated communities, and among people skittish about receiving two doses.