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J&J COVID-19 vaccine pause: What to know if you received shot, have future appointment and more

On Tuesday, U.S. officials recommended a "pause" on the use of the Johnson & Johnson COVID-19 vaccine in order to investigate U.S. reports of a rare type of blood clot following vaccination.

Nearly 7 million J&J doses have been administered in the U.S., almost all without serious side effects. Now, the millions of people who have received the shot - and those who have been scheduled to - are left with many questions surrounding the safety of the vaccine. 

Here are some answers to common questions about the Johnson & Johnson COVID-19 vaccine and the recommended "pause" by the U.S. government.

Why did U.S. officials pause the J&J COVID-19 vaccine?

On Tuesday, the Centers for Disease Control and Prevention and the Food and Drug Administration recommended a "pause" in using the single-dose Johnson & Johnson COVID-19 vaccine while they investigate reports of potentially dangerous blood clots.

The blood clots have been reported in six patients who received the J&J shot. All were women between the ages of 18-48 and officials said they presented symptoms 6-13 days after getting the shot. 

U.S. officials confirmed Tuesday one of the patients had died and another was in critical condition.

In addition to the investigation, regulators say the "pause" is to help educate patients and medical professionals about identifying and treating the clots. The clots were observed along with reduced platelet counts, making the usual treatment for blood clots, the blood thinner heparin, potentially "dangerous."

Officials stressed Tuesday in a media briefing that pausing the J&J vaccine is a recommendation - not a mandate - and that it is recommended out of an extreme abundance of caution. 

"These events appear to be extremely rare, however, COVID-19 vaccine safety is a top priority for the federal government and we take all reports of adverse events following vaccination very seriously," said Janet Woodcock, the Acting FDA Commissioner. 

RELATED: US recommends ‘pause’ on Johnson & Johnson COVID-19 vaccine to investigate rare clotting reports

What causes the blood clot?

Officials don’t have a definitive cause yet for why these rare blood clots can occur, but they did offer speculation that it has to do with the individual’s immune response. 

"The probable cause that we believe may be involved here, that we can speculate, is a similar mechanism that may be going on with other adno viral vector vaccines. That is that, this is an immune response that occurs very, very rarely after some people receive the vaccine. That immune response leads to activation of the platelets and these extremely rare blood clots," said Peter Marks, Director of the FDA Center for Biologics Evaluation and Research.

"The person being vaccinated makes an immune response, potentially, that actually involves their own platelets or other parts of the coagulation system and can cause this problem. That’s the leading theory or hypothesis," echoed Janet Woodcock, the Acting FDA Commissioner. 

The specific type of blood clot that's being investigated is a cerebral venous sinus thrombosis (CVST) in combination with the reduced blood platelets. 

What are symptoms of the blood clot? 

U.S. health regulators are recommending that people who experience severe headache, abdominal pain, leg pain or shortness of breath within three weeks after receiving the J&J shot should contact their health care provider.

The risk for the rare clotting remains low for those who received the J&J shot more than a month ago and did not experience such symptoms.

Officials also noted that these symptoms associated with blood clotting are different from the normal, flu-like side effects that some experience after getting a COVID-19 vaccine.

What do doctors need to know about the J&J COVID-19 vaccine?

The FDA and CDC are currently investigating the reports of these rare cases and recommended the J&J vaccine pause out of an abundance of caution.

"This is important, in part, to ensure that the health care provider community is aware of the potential for these adverse events and can plan for proper recognition and management due to the unique treatment required with this type of blood clot," the agencies said in the joint statement. 

Treatment of this specific type of blood clot is different from the treatment that might typically be administered, the blood-thinner heparin. 

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

Healthcare providers are asked to report any adverse events to the Vaccine Adverse Event Reporting System.

What should I do if I have an appointment to get the J&J vaccine?

Many states announced Tuesday in the hours after the recommendation that they won’t administer the J&J COVID-19 vaccine and will offer a different shot instead. 

For example, top county officials in Houston and Dallas said Pfizer or Moderna vaccines will be offered instead of Johnson & Johnson at their large vaccination sites.

Dr. Anne Schuchat, the principal deputy director at the CDC also said Tuesday that its agency partners are working to reschedule people who have J&J vaccine appointments in the coming days ahead. 

Dr. Peter Marks, the Director of the FDA Center for Biologics Evaluation and Research, also said Tuesday that if patients have an individual appointment with their healthcare provider to get the J&J shot, they could still discuss the benefit-risk factor and make an individualized determination on whether to receive the shot or not. 

"This is a recommendation, not a mandate," he said. 

How long will the pause of the J&J COVID-19 vaccine last?

FDA Acting Commissioner Janet Woodcock said Tuesday at a news conference that the pause of the J&J vaccine in the U.S. is expected to last "a matter of days."

The CDC’s Advisory Committee on Immunization Practices (ACIP) will meet Wednesday to further review these cases and "assess their potential significance," the agencies said. 

The FDA has also launched an investigation into the cause of the clots and low platelet counts.

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

Are the other COVID-19 vaccines still safe?

CDC's Dr. Anne Schuchat said authorities have not seen similar reports of clots after use of the Pfizer or Moderna vaccines, which were developed using a different mRNA technology than the J&J shot. Schuchat emphasized that people should continue to get vaccinated with those shots.

To date, nearly 183 million doses of both Pfizer and Moderna have been administered in the U.S. Both were found to be both safe and effective at preventing COVID-19 in large clinical trials, as well as growing evidence in real-world conditions as the vaccines are distributed worldwide.

Moderna released its own statement following news of the J&J pause in the U.S., echoing that there has been no such association with its two-dose vaccine and the rare blood clotting cases after more than 64.5 million doses administered globally.

The J&J vaccine first received emergency use authorization from the FDA in late February. To date, more than 6.8 million doses of the J&J vaccine have been administered in the U.S. — with the vast majority experiencing no or mild side effects, which are normal.

Is this similar to what’s happening in Europe with the AstraZeneca vaccine?

Until now, concern about rare and 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 reports appear similar to the blood clots seen among the six women in the U.S. but officials haven’t said yet that they’re the same. 

Janet Woodcock, Acting FDA Commissioner, said the FDA has been in "constant contact" with regulators worldwide to look at adverse effects from all COVID-19 vaccines. 

The J&J and AstraZeneca vaccines are made with the same technology. Other leading COVID-19 vaccines train the body to recognize the spike protein that coats the outer surface of the coronavirus, while 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 Detroit and Cincinnati.