Two reports published in a leading medical journal on Friday help explain how AstraZeneca’s COVID vaccine can in rare cases cause serious, sometimes fatal, blood clots.
Researchers in Germany and Norway have found that people who develop a thrombus after vaccination produce antibodies that activate their platelets, the blood clot that participates in the thickening process. The new reports add to the details of what researchers have already publicly stated about the blood disorder.
It is not known why the rare reaction occurred. Younger people seem more sensitive than older people, but researchers say there are no preconditions for health that may be predisposed to the problem, so there is no way to tell if an individual is at high risk.
Reports of thrombosis have led some countries to limit the AstraZeneca vaccine in the elderly or to discontinue its use altogether. The incidents dealt a crushing global effort to stop the epidemic as AstraZeneca’s filming, an easy-to-keep և relatively inexpensive, vaccination program, became the backbone of more than 100 countries.
Regulators in Europe have emphasized that coagulation disorders are rare and that the benefits of the vaccine outweigh the risks. But while the side effects can be devastating or fatal, such as the blood clots in the brain associated with this vaccine, some sections of society: consider the risk unacceptable, even if it is extremely rare.
As of Sunday, European regulators had reported 222 rare cases of blood clots in the և 30 տնտեսական European Economic Area (EU plus Iceland, Norway and Liechtenstein). They say about 34 million people in those countries have received the AstraZeneca vaccine, a coagulation problem that occurs in about one percent of the 100,000 recipients.
European regulators say they have conducted a detailed investigation into 86 cases as of March 22, 18 of which were fatal.
Vaccine safety marks are high because they are given to healthy people. Of particular concern is the seemingly greater vulnerability of young people to coagulation disorders, as their risk of developing COVID is lower than that of older people. These differences suggest that, in general, young people may gain less and lose more from the AstraZeneca vaccine than older people.
Germany, the Netherlands, the Philippines, Portugal և Spain have recommended that the AstraZeneca vaccine be given only to people over 60 years of age. Canada ան France restricted it to persons over 55 years of age; Australia, over 50; Belgium – over 56 years old. Britain, where the vaccine was developed, has been its toughest advocate, but on Wednesday said it would start offering alternatives to people under 30.
Cameroon, Democratic Republic of the Congo, Denmark և Norway have stopped using the vaccine.
A full dose of the AstraZeneca vaccine requires two doses, but regulators in France have advised people under the age of 55 who have had one dose to get other vaccines for a second dose.
The AstraZeneca vaccine is not approved for use in the United States, but the Food and Drug Administration is reviewing it to see if it should be.
The European Medicines Agency said Wednesday that vaccine labeling should be reviewed, including thrombosis as a “very rare” side effect of the vaccine.
In a statement posted on its website, AstraZeneca said it was “actively working with regulators to make these changes to product information; it is already working to understand individual cases, epidemiology, and possible mechanisms that may explain these extremely rare events.”
Two new reports were published in The New England Journal of Medicine. One from Germany describes 11 patients, including nine women aged 22 to 49 years. Within five to 16 days of vaccination, they were found to have one or more blood clots. Nine had cerebral venous thrombosis, a mucous membrane that blocks the outflow of blood from the brain. Some had blood clots in their lungs, abdomen, or other areas. Six of the 11 died, one from a brain haemorrhage.
One of the patients had pre-existing conditions that affected the clotting, but Dr. Andreas Greinacher, the report’s author, told reporters at a briefing on Friday that those conditions probably only played a minor role in the post-vaccination disorder.
All patients, including 17 patients with thrombosis after vaccination, whose blood was tested had antibodies known to activate platelets.
Antibodies lead to a condition called thrombotic thrombocytopenia, which causes both thickening and abnormal bleeding. The researchers suggested that these patients be called “vaccine-induced immune thrombocytopenia.”
The article describes specialized blood tests that can be used to diagnose the disorder, and suggests treating it with a blood transfusion called an intravenous immune globule, which is used to treat various immune disorders. Drugs called anticoagulants or blood thinners may also be used in some cases, but not commonly used, heparin, as the vaccine-related condition is very similar to a disease that is rare in heparin recipients.
The second report, from Norway, described five patients, one male, four female health workers, 32 to 54, who had a blood clot and were bleeding seven to 10 days after receiving the AstraZeneca vaccine. Four had severe brain thrombi, and three died. Acute headaches were one of their early symptoms. Like German patients, they all have high levels of antibodies that can activate platelets.
The team from Norway also recommended treatment with intravenous immune globulin. The researchers said the disorder was rare, but “a new phenomenon with a devastating effect on otherwise healthy young adults,” suggesting it may be more common than previous studies with the AstraZeneca vaccine.
On Friday, European regulators said they were reviewing reports of several cases of blood clots in people who received the onsone և John onson vaccine. In the United States, federal agencies are investigating reports of a variety of unusual blood disorders associated with abrupt platelet counts that have occurred in several people who have received either the Pfizer-BioNTech or Moderna vaccines.