By Peter Loftus and Thomas M. Burton 

U.S. health authorities recommended a pause in the use of Johnson & Johnson's Covid-19 vaccine in order to investigate rare but severe cases of blood clots, a setback to vaccination efforts racing against virus variants.

The U.S. Food and Drug Administration and the U.S. Centers for Disease Control and Prevention announced the move Tuesday, after finding that six women between the ages of 18 and 48 years who got the vaccine had developed blood clots and one died. More than 6.8 million doses have been administered in the U.S., the agencies said.

The decision prompted the U.S. government to suspend at its vaccination sites administration of J&J's vaccine, a federal health official said, while states and other authorities scrambled to adjust.

The government's review may only take a few days, health authorities said. A panel of outside experts will meet Wednesday to review the matter for the CDC, while the FDA will also conduct an investigation.

J&J said Tuesday it is aware of an extremely rare disorder involving people with blood clots in combination with low platelets in a small number of people who received its vaccine. J&J said it is working with health authorities and medical experts.

The company also said it has decided to delay the rollout of its vaccine in Europe, which had been planned for later this month.

President Biden's Covid-19 coordinator Jeff Zients on Tuesday said a recommended pause in the administration of the J&J vaccine was "out of an abundance of caution" and won't have a major effect on vaccination efforts.

J&J's vaccine "makes up less than 5% of the recorded shots in arms in the United States to date," Mr. Zients said.

He also said the administration was working with state and federal partners to get people who were scheduled to receive the J&J shot signed up for a Pfizer or Moderna vaccine.

Mr. Zients said the White House learned that the FDA and CDC were recommending a pause in the administration of the J&J vaccine on Tuesday morning when it was made public.

He said the White House was told Monday night an announcement would be coming in the morning but was unaware of its contents. "There was no heads up here," Mr. Zients said.

The halt comes at a dangerous time during the pandemic, as health authorities race to vaccinate as many people as possible before variants develop that can evade the shots. Among the biggest hurdles is overcoming hesitancy to get vaccinated.

The specter of blood clots could add to concerns about the safety of the shots, though vaccines from Pfizer Inc. and its partner BioNTech SE and from Moderna Inc. have proven relatively safe so far.

Pause of the J&J's vaccine use could hurt some vaccination efforts in the U.S., especially in areas that lacked the special freezers required to store the two-dose Pfizer-BioNTech and Moderna shots and on college campuses that wanted to give their students the single J&J dose.

Yet the impact could be limited because Pfizer and Moderna have been ramping up production as they gained more experience making the shots and expanded their manufacturing capabilities. Federal officials expected to allocate about 26.5 million doses of the Pfizer-BioNTech and Moderna vaccines combined this week, compared with 1.5 million of J&J's.

The U.S. has an abundant supply of the Pfizer-BioNTech and Moderna vaccines, a Health and Human Services Department official said. The J&J vaccine won't be given at federally-run vaccination sites, the official said.

Some states and vaccine providers quickly made alternative plans in response to the call for a pause by federal health officials. New York Gov. Andrew Cuomo tweeted that state-run mass vaccination clinics would offer the Pfizer-BioNTech vaccine in lieu of the J&J vaccine to people with appointments Tuesday.

Walgreens Boots Alliance Inc. said it immediately suspended administration of J&J's vaccine at its retail pharmacies and off-site clinics and will await further guidance. The company is reaching out to people who had appointments to reschedule them.

Separately, Australian health officials said Tuesday the country has decided against using J&J's shot, after a panel of scientific experts advising the government said it shouldn't buy any more vaccines of its type.

Johnson & Johnson's vaccine has been expected to account for more than 15% of the European Union's second-quarter deliveries, or 55 million of 360 million expected doses, during the three months from March through June. European health authorities have been looking into the clotting issue. Deliveries of J&J shots to the continent began Monday.

The EU's European Medicines Agency, which has closely analyzed concerns about blood clots among recipients of the AstraZeneca vaccine, is also studying clot concerns about the J&J vaccine.

J&J's vaccine was the third authorized for use in the U.S. It uses similar technology as a vaccine from AstraZeneca PLC and the University of Oxford, not yet authorized in the U.S. that has also been linked to rare cases of blood clots.

The J&J and AstraZeneca viral-vector vaccines contain a virus that causes the common cold, but which has been rendered harmless. That virus is engineered to include genetic instructions that set off an immune response to protect people against the coronavirus.

The Pfizer and Moderna vaccines use a different technology, called messenger RNA, to achieve the same goal.

The risk of these rare types of blood clots is likely to be a "class effect" of viral-vector vaccines, said Dr. Paul Offit, director of the vaccine education center at Children's Hospital of Philadelphia. He said it is possible they are causing immune-system antibodies against a protein, a process that can lead to clots.

J&J's vaccine is given in one dose, whereas the Pfizer and Moderna shots are given as two doses, three or four weeks apart.

In the case of J&J's shot, six women ages 18 to 48 developed blood clots after taking the J&J vaccine, the FDA and CDC said. The clots developed 6 to 13 days after vaccination. The women also had in their blood low counts of platelets, which help with clotting.

Given the nature of the side effect, doctors shouldn't use the normal course of clotting treatment, involving a drug called heparin, the FDA and CDC said. "In this setting, administration of heparin may be dangerous, and alternative treatments need to be given," they said.

The agencies said people vaccinated with J&J's vaccine should notify their doctor if they develop severe headache, abdominal pain, leg pain, or shortness of breath within three weeks after vaccination.

Dr. Janet Woodcock, the FDA's acting commissioner, said during a press briefing the time frame of the pause in vaccination will be "a matter of days." Dr. Peter Marks, the FDA's top vaccine official, said officials haven't determined a definitive cause, but the vaccine may be causing a rare immune response affecting blood platelets.

Dr. Marks said there have been over 180 million doses of the Moderna or Pfizer vaccines administered, and that such events haven't been reported.

Clots can be life-threatening, even fatal, if they choke off blood and therefore oxygen flow to the brain or heart. The type of blood clot seen in some people receiving the J&J vaccine was called a cerebral venous sinus thrombosis, which can prevent blood from draining out of the brain and can lead to a hemorrhage.

Dr. Marks said that such clots normally only occur in between two and 14 per million people. But seeing such clots along with low platelet levels "create a pattern" similar to that in Europe with the AstraZeneca vaccine.

Like other Covid-19 vaccine makers, J&J, of New Brunswick, N.J., developed its shot much more quickly than it usually takes to develop a vaccine, given the urgency of the pandemic. The company began work in early 2020 and started testing the vaccine in people in July.

Certain types of blood clots were seen in a small number of subjects in the large clinical trial of J&J's vaccine that supported its authorization in late February. The FDA said there wasn't enough evidence at the time to determine whether the vaccine was causing the clots, but said it would monitor the situation.

J&J paused the large study of its vaccine in October because one vaccine recipient had a type of blood clot called a transverse sinus thrombosis resulting in a brain hemorrhage, according to an FDA document. J&J investigated and found that it wasn't related to the vaccine, and resumed the study.

J&J also has had problems manufacturing its vaccine. A batch of the vaccine's main ingredient that was being made at a contractor's plant in Baltimore was recently ruined by contamination, and no doses were distributed from the batch. Health regulators still haven't authorized the plant where the mishap occurred, hurting J&J's ability to churn out more doses.

Mass vaccination clinics administering the J&J vaccine in North Carolina, Colorado and Georgia have closed temporarily in recent weeks after some people receiving the shot experienced adverse effects. It wasn't immediately clear whether the vaccine caused them.

Earlier this month, U.K. health authorities recommended against giving AstraZeneca's shot to people under 30 years after receiving reports of rare but deadly blood clots. Countries including Canada and Germany have also restricted use.

The link between the vaccine and the clotting incidents is still unclear. Scientists in Germany and Norway said the vaccine may cause an autoimmune reaction that leads to clots in the brain.

--Daniel Michaels and Sabrina Siddiqui contributed to this article.

Write to Peter Loftus at peter.loftus@wsj.com and Thomas M. Burton at tom.burton@wsj.com

 

(END) Dow Jones Newswires

April 13, 2021 13:41 ET (17:41 GMT)

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