"It just doesn't happen in healthy people out of the blue and that's what's happening," said Dr. Hanny Al-Samkari, a hematologist and clinical investigator at the Massachusetts General Hospital.
But the risks are unexpected, unusual and might be reduced with the proper response or by limiting who gets the vaccine, Marks said.
"Our ultimate goal here is to get as many people vaccinated with a safe and effective vaccine as we can," he said, "but we feel like we have to take action."
The condition is believed to be the same one seen in Europe with a similar vaccine made by AstraZeneca and Oxford University. That vaccine, which is not available in the United States, has been linked to more than 220 unusual clotting cases as of April 4, out of 34 million doses delivered.
Most of the time, it's difficult to directly connect a serious health problem with a vaccine, but with the J&J and AstraZeneca-Oxford vaccines, "there is a smoking gun," said Dr. Theodore Warkentin, who co-authored an April 9 paper describing unusual blood clotting conditions in 11 patients who received the AstraZeneca-Oxford vaccine.
Warkentin and his colleagues named the condition vaccine-induced immune thrombotic thrombocytopenia or VITT. It is believed to be similar to a rare problem seen either in patients recovering from surgery or from those on heparin, said Warkentin, a hematologist at McMaster University in Ontario, Canada..
In all cases, the immune system creates antibodies that activate platelets in the bloodstream, he said. The platelets, which normally promote wound healing, end up clumping and causing blood clots, often in the brain.
The diagnosis of VITT may be challenging, because typical tests for blood clots can come back negative and doctors will have to look specifically for toxic antibodies, said Anand Padmanabhan, an expert in a similar condition called heparin-induced thrombocytopenia at the Mayo Clinic.
People with suspected VITT should not be given the blood thinner heparin, because it could exacerbate the problem, Padmanabhan said.
All six of the people diagnosed with rare clots after receiving the J&J vaccine were relatively young women – but that doesn't mean that men and people who are older can't develop the condition, Marks warned.
"It's a question of whether this is the tip of the iceberg," she said. "Are we just seeing the start of case reports in the U.S. and are we going to see more?"
"If you mistreat it, people die," she said, "and if you don't treat it, there's still a high mortality associated with it."
But it can be successfully treated if doctors are looking for it.
"If you're not aware it can happen or you're not looking for it, it may go undiagnosed," she said.
Blood thinning drugs other than heparin can be useful for VITT patients, Warkentin said.
"Whenever there is a concern about the vaccine, they put a hold on it," Al-Samkari said. "That's appropriate and we want that to happen.
https://www.usatoday.com/story/news/...es/7212193002/
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