They say in some cases, the shot can trigger inflammation, which causes the body to overproduce platelets, leading to clotting.
The team says that if their hypothesis is correct, the reaction can be identified and easily treated by medical professionals.
It comes on the heels of news that Canada is suspending use of the vaccine for people under age of 55 due to blood clot fears
The researchers say the phenomenon is similar to one that seldom occurs with a condition called heparin-induced thrombocytopenia (HIT) when sufferers take a drug called heparin.
Among those with HIT, the drug triggers the immune system to produce antibodies that activate platelets.
Drugs other than heparin can cause clotting disorders that strongly resemble HIT, and researchers suspect that in rare cases, the AstraZeneca vaccine may be another such trigger.
Earlier this month, there were about 30 cases of blood clotting among patients after receiving a dose of the vaccine, with a few resulting death.
German researchers found signs of a type of antibody that forms in response to inflammation in some people and attacks platelets in nine people who developed clots after getting the AstraZeneca shot. These antibodies destroy the platelets and, to make up for the loss, the body overproduces platelets, causing them to clot (file)
It led to more than a dozen countries pausing their use of the vaccine, despite the European Medicines Agency declaring the benefits of the shots outweighed the risks.
In a study, published on
Seven patients had cerebral venous thrombosis (CVT), which is a blood clot in the brain; one had a pulmonary embolism, and one had CVT had splanchnic vein thrombosis, which occurs when a vein in the abdomen clots.
Blood samples from four of the individuals showed they had the same kind of antibodies that activate platelets and initiate clotting in HIT.
These samples were then compared to 20 individuals who were given the AstraZeneca vaccine and did not experience blood clots.
None of this group has these antibodies,
The researchers advise anyone receiving the AstraZeneca vaccine to keep an eye out for any bruising, swelling or headaches that begin four or more days after being immunized.
If vaccine recipients identify any of these symptoms early on, the situation can be treated easily by a doctor.
Meanwhile, a group of researchers in Norway say have been studying three cases of blood clots post-AstraZeneca vaccination.
Professor Pål Andre Holme of Oslo University Hospital told Norwegian newspaper
‘Our theory that this is a strong immune response that most likely comes after the vaccine,’ Holme said, according to an
‘There is no other thing than the vaccine that can explain this immune response.’