Johnson & Johnson pauses COVID-19 vaccine trial after US recommends investigation of rare clotting reports

Johnson & Johnson said it will pause its ongoing vaccine trial after federal health officials on Tuesday recommended a "pause" on the use of its COVID-19 vaccine in order to investigate reports in the U.S. of a rare type of blood clotting following vaccination.

"The safety and well-being of the people who use our products is our number one priority. We are aware of an extremely rare disorder involving people with blood clots in combination with low platelets in a small number of individuals who have received our COVID-19 vaccine," Johnson & Johnson said in a statement. "The United States Centers for Disease Control (CDC) and Food and Drug Administration (FDA) are reviewing data involving six reported U.S. cases out of more than 6.8 million doses administered. Out of an abundance of caution, the CDC and FDA have recommended a pause in the use of our vaccine."

"In addition, we have been reviewing these cases with European health authorities. We have made the decision to proactively delay the rollout of our vaccine in Europe and pause vaccinations in all Janssen COVID-19 vaccine clinical trials while we update guidance for investigators and participants," the statement continued.

"We have been working closely with medical experts and health authorities, and we strongly support the open communication of this information to healthcare professionals and the public."

Dr. Anthony Fauci, the nation’s top infectious disease expert, said Tuesday the pause of J&J's vaccine "really doesn't mean anything" about the effectiveness of the shot for the people who have already received it. To date, more than 6.8 million doses of J&J's single-dose shot have been administered in the U.S. with the vast majority experiencing no or mild side effects.

Fauci noted the more than 120 million Americans who have gotten at least one dose of a COVID-19 vaccine — the vast majority receiving either Pfizer or Moderna’s shots — are healthy and called the J&J blood clot news a "really rare event."

"There have been no red flag signals from those. So you’re talking about tens and tens and tens of millions of people who have received vaccines with no adverse effect," Fauci said during a White House press briefing. "If you look at what we know so far, there have been six out of the 6.8 million doses, which is less than one in a million."

The clots were reported in six women approximately 6 to 13 days after receiving a J&J vaccination, in combination with low platelet counts. All six cases were between the ages of 18 and 48, and there was one death officials confirmed during a press call.

The U.S. Food and Drug Administration and U.S. Centers for Disease Control and Prevention said in a joint statement earlier Tuesday that the pause of the single-dose vaccine is "out of an abundance of caution" while the agencies investigate the cases.

"I’d like to stress these events appear to be extremely rare. However COVID-19 vaccine safety is a top priority," FDA Acting Commissioner Janet Woodcock said at a news conference. "We expect it to be a matter of days for this pause."

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CDC's Dr. Anne Schuchat said authorities have not seen similar reports of clots after use of the Pfizer or Moderna vaccines, and that people should continue to get vaccinated with those shots.

In response to the pause on the Johnson & Johnson vaccine, Pfizer announced on Tuesday that with over 200 million doses of its vaccine administered, there has been no evidence to suggest any blood clotting similar to cases found in J&J vaccine recipients.

In the joint statement, U.S. health authorities said treatment for this rare and specific type of blood clot is different from the treatment that might normally be administered, and they sought to get the word out to health providers. They cautioned doctors against using a typical clot treatment, the blood-thinner heparin. 

"In this setting, administration of heparin may be dangerous and alternative treatments need to be given," the FDA and CDC said.

For people who received the J&J vaccine more than a month ago, the agencies said the risk of this rare clotting remains "low." The agencies recommend that people who received the shot within the last three weeks and are experiencing severe headache, abdominal pain, leg pain or shortness of breath contact their doctor.

U.S. federal distribution, including mass vaccination sites, will pause the use of the J&J shot, and states and other providers were expected to follow. Moderna and Pfizer, the other two vaccines with emergency use authorization in the U.S., are not affected by the pause. 

COVID-19 Response Coordinator Jeff Zeints said the U.S. has enough supply of both Pfizer and Moderna to stay on track for all Americans who want to get vaccinated by May 31 to do so. Zients added that the country is also well on pace to meet President Joe Biden’s goal of 200 million shots administered by his 100th day in office later this month. 

The CDC’s Advisory Committee on Immunization Practices (ACIP) will meet Wednesday "to further review these cases and assess their potential significance," the statement said. The FDA has also launched an investigation into the cause of the clots and low platelet counts.

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The vaccine received emergency use authorization from the FDA in February, adding additional hope in the fight against the virus due to its single-dose and simple storage requirements — potentially allowing quicker vaccinations across the country.

But to date, the shot only makes up a small fraction of the vaccines administered in the U.S. as the company has been hit with production delays and manufacturing errors at a production facility in Baltimore. J&J has committed about 100 million doses to the U.S. government by the end of May, and last week the drugmaker took over the facility to scale up production.

Until now concern about the unusual blood clots has centered on the vaccine from AstraZeneca, which has not yet received authorization in the U.S. Last week, European regulators said they found a possible link between the shots and a very rare type of blood clot that occurs together with low blood platelets, one that seems to occur more in younger people.

The European Medicines Agency stressed that the benefits of receiving the vaccine outweigh the risks for most people. But several countries have imposed limits on who can receive the vaccine. Britain recommended that people under 30 be offered alternatives.

RELATED: Johnson & Johnson expands COVID-19 vaccine trial to include ages 12 to 17

The J&J and AstraZeneca vaccines are made with the same technology. Leading COVID-19 vaccines train the body to recognize the spike protein that coats the outer surface of the coronavirus. But the J&J and AstraZeneca vaccines use a cold virus, called an adenovirus, to carry the spike gene into the body. J&J uses a human adenovirus to create its vaccine while AstraZeneca uses a chimpanzee version.

This story was reported from Cincinnati. The Associated Press contributed.