J&J Covid-19 Vaccine Pause Over Blood-Clot Fear Heads to Review

Many public-health authorities, however, contend that the benefits of the vaccine outweigh the risks. Anthony Fauci, President Biden’s chief medical adviser, has predicted the U.S. pause would end as soon as Friday, perhaps with new restrictions or warnings.

The Advisory Committee on Immunization Practices, which includes doctors and public-health officials, is expected to advise the Food and Drug Administration and Centers for Disease Control and Prevention to either continue or lift the pause after a meeting Friday.

A recommendation to lift the pause—and agreement by the FDA and CDC—could put the vaccine back in circulation as early as this weekend, because millions of doses have already been distributed to vaccine sites.

The lifting of the pause could be accompanied by restrictions limiting the vaccine’s use to older adults, as well as possible warnings about the potential clot risk, according to people familiar with the matter.

The ACIP meeting is scheduled to begin at 11 a.m. Eastern time, with a potential vote by 5 p.m.

It will be the ACIP’s second emergency meeting in 10 days to discuss the J&J vaccine. The committee, which advises the CDC, met April 14, one day after use of J&J’s vaccine was paused. But the committee, meeting online, deferred voting on a recommendation because members wanted more information about the vaccine’s risks and benefits.

European health regulators also have investigated the clot risk and determined that vaccinations can proceed once J&J resumes rolling out its vaccine there, but that product information should carry a warning of the rare clot risk. The European Medicines Agency said the benefits of the vaccine outweigh its risks.

J&J is updating its package information for the vaccine in Europe to include details about the clot condition, and how to identify and treat it.

Initially, six women between the ages of 18 and 48 were reported to have clots in vessels that drain blood from the brain, combined with low counts in the blood of platelets, which help with clotting. That rare combination appeared to occur among J&J vaccine recipients at a higher rate than what would be expected in the general population, a CDC official said at the first ACIP meeting. Health officials have since identified three more cases.

At the time of last week’s pause in vaccinations, more than seven million people had received J&J’s vaccine since it was authorized for use in the U.S. in late February. A large study of the single-dose vaccine showed it was about 66% effective at preventing moderate-to-severe Covid-19 disease.

J&J has said it has been investigating the cases, and while the clot condition is a potential risk, as of late last week J&J said there wasn’t sufficient evidence to establish that its vaccine was causing the rare events.

The Food and Drug Administration authorized use of J&J’s vaccine in late February, the third Covid-19 shot to be cleared—after shots from Pfizer Inc. with its partner BioNTech SE, and Moderna Inc.

Before the pause, J&J’s vaccine made up a relatively small portion of all available Covid-19 vaccine doses, as the company was increasing production.

Still, public-health officials view the J&J vaccine as particularly useful in vaccinating hard-to-reach populations, such as the homebound and homeless. It doesn’t require a second dose like the Pfizer and Moderna vaccines do, and it can be stored in a standard refrigerator for longer periods than the other vaccines.

The company has a federal contract to supply about 100 million doses of its vaccine for U.S. use by midyear. J&J has said it is committed to supply that amount, but that production issues at a contract manufacturer’s plant in Baltimore could affect timing of the delivery of doses. Production of J&J’s vaccine at the plant recently stopped during an FDA inspection, which identified unsanitary conditions and other problems that must be addressed.

A significant issue that the ACIP might consider on Friday: how the clot risk among J&J vaccine recipients stacks up against the risk of clots that come with Covid-19 itself.

The risk of blood clots is much higher from Covid-19 disease than from the vaccines associated with these complications, said Jean Connors, a hematologist at Brigham and Women’s Hospital in Boston. Blood clotting all over the body is one complication of severe forms of the disease. About 15% to 20% of Covid-19 patients who are admitted to intensive-care units develop blood clots, Dr. Connors said.

Use of the vaccine is even more urgent now with Covid-19 case numbers rising rapidly in some other countries, such as India and Brazil, she said. “The devastation due to Covid infection in these countries is catastrophic,” Dr. Connors said.

Cerebral venous sinus thrombosis—blood clots in the brain—alone affects five out of every one million people a year, according to data cited by the American Heart Association. It is far more common in women, and strikes most often in the third decade of life, hematologists say.

The incidence of cerebral blood clots as a result of Covid-19, on the other hand, is 39 for every one million people in the two weeks after a Covid-19 diagnosis, according to a paper by Oxford researchers that was posted on a preprint server, meaning that it hasn’t been peer-reviewed.

Awareness by physicians of the blood-clotting condition associated with the vaccine and how to treat it quickly and appropriately will help reduce illness and death from it, Dr. Connors said. Four of the first six patients who developed clotting and low platelets after vaccination were treated with heparin, which can worsen their condition. Health authorities now say nonheparin blood thinners should be used to treat these patients.

“Now that we are aware of this syndrome, the risks of dying from it are lower as we believe that we can more quickly identify those that have it and treat it appropriately,” Dr. Connors said.

Write to Peter Loftus at [email protected] and Betsy McKay at [email protected]