Rare cases of coagulation seen with two Covid-19 vaccines have put the spotlight on an unusual reaction that occurs when the body unleashes its immune system firepower against platelets.
Health officials investigate whether and how the immune response can occur in people who have been vaccinated by AstraZeneca Plc en Johnson & Johnson. Concerns have risen so high that the U.S. Centers for Disease Control and Prevention and the Food and Drug Administration jointly recommended a break in the use of the J&J vaccine on Tuesday.
The syndrome is highly uncommon in that it involves increased clotting, as well as low levels of platelets, the blood component that is primarily responsible for clotting, and has only been seen at low doses in vaccines. The pressure is on governments that want to immunize millions of people over the next few months to understand the risk and avoid panic.
“The most challenging issue is how we can provide responsible and proper communication to the public,” said Behnood Bikdeli, a cardiologist at Harvard Medical School and Brigham and Women’s Hospital, who studies coagulation and Covid. “We want to be transparent, but we want to make sure our people are not out of proportion. On the order of magnitude, the problem is Covid. ”
Adenovirus link
The occurrence of severe, difficult-to-predict blood clotting events in two leading vaccines is a setback in the race to vaccinate as many people as possible before next winter. This raises the possibility that some of the vaccines on which global stock is delivered could place significant restrictions on them that could limit their use, as is already the case with AstraZeneca’s vaccine in Europe.
The Astra and J&J vaccines both use an adenovirus to help the immune system identify and fight the coronavirus. Other similar vaccines, the Russian Sputnik V-shot and one from China CanSino Biologics Inc., can also be explored.
CanSino said it uses a different kind of adenovirus vector than Astra or J&J. There have been no reports of serious blood clots among the 1 million people who received the shot, the company said in a Hong Kong stock exchange filing.
Read more: Blood clots, Anaphylaxis and other vaccines
Six women aged 18 to 48 had a type of blood clot in the brain called cerebral venous sinus thrombosis after receiving the J&J vaccine, health officials said Tuesday, with one woman dead and another in a critical condition. The patients all had low blood platelets, a suspicious resemblance to a complication observed with the AstraZeneca vaccine and the University of Oxford.
It is also similar to another rare clotting disorder that occurs in people treated with heparin. While the anticoagulant is normally used to prevent blood clots, in rare cases it will switch the immune system against a platelet protein, leading to dangerous lowering of the levels and significant clotting.
What Bloomberg Intelligence says:
‘The CDC is doing the right thing despite the fact that this rare blood clotting event is at a very low rate of 1 per million, against. AstraZeneca is 1 per 100,000. The US has more than enough doses of Pfizer-BioNTech and Moderna to cover its adult population by July. But the rest of the world has reopening economies against. use vaccines with rare side effects. ”
– Sam Fazeli, senior pharmaceutical analyst at BIClick on here to read the research.
Both the Astra and the J&J vaccines are likely to cause platelet antibodies, leading to platelet activation and cerebral blood clots in rare cases, says Peter Jay Hotez, an immunization expert at Baylor College of Medicine in Houston.
“Each province will have to make decisions to continue” with the use of the vaccines, or to decide on restrictions on their use, “he said. ‘This is a problem for Africa and Latin America’, as the countries were heavily dependent on adenovirus vaccines.
Heparien Kommer
People with the vaccine should probably not get heparin Jeff Weitz, a professor at McMaster University and president of the International Society on Thrombosis and Hemostasis. Other options such as Eliquis of J & J’s Xarelto by Bristol-Myers Squibb Co. is probably safer oral medicine, he said.
The discontinuation of the J&J vaccine will give CDC and FDA time to review the situation and make sure doctors who see the clotting syndrome know how to react, he said. Peter Marks, director of the FDA’s Center for Biological Evaluation and Research. The events were seen between 6 and 13 days after vaccination and were identified by the FDA through a system reported by the government through the vaccine, Marks said in a webinar sponsored by the American Medical Association.
“Everyone knew it could boost the confidence of vaccines,” he said. Although the cases ‘could only be a statistical deviation’, the health authorities tried to exercise abundant caution.
Safety issues have emerged with other Covid vaccines that clinicians have learned to tackle, he said. For example, after a number of cases of anaphylaxis, a severe allergic reaction, were linked to mRNA vaccines, the health authorities educated doctors about treatment.
Read more: US calls for interruption of J&J shot on blood clots, roiling Roll out
Researchers think that the blood clots may be caused by a rare autoimmune reaction against the vaccine that leads to unusually low platelets and severe blood clots. Just as heparin can make the immune system sensitive to platelets in rare cases, the vaccines can cause a similar reaction.
The blood clots associated with the vaccine are “very rare” and appear with a very unusual clotting pattern in the head or abdomen. Mark Crowther, a hematologist and chair of the Department of Medicine at McMaster.
Unlike a stroke, where blood vessels in the brain are blocked, with the vaccine-related blood clots, the veins that drain blood from the head are blocked, Crowther said. He is also an officer of the American Society of Hematology. This is one of the reasons why patients often report severe headaches, he said.
In two studies published in the New England Journal of Medicine on April 9, a research team in Norway and another group in Germany and Austria found that patients with severe coagulation reactions to the AstraZeneca vaccine had antibodies to an important coagulation protein. called platelet factor 4.
New phenomenon
Six of the 11 blood clots reported by German and Austrian researchers were fatal, while three of the five people with blood clots studied by Norwegian scientists died, according to the New England Journal of Medicine studies.
The blood clotting disorder ‘is a new phenomenon with devastating consequences for otherwise healthy young adults’, the Norwegian researchers from the Oslo University Hospital concluded.
Clotting tips may have arisen during J & J’s final tests. In a report to the FDA, J&J said that a 25-year-old male test volunteer in his phase 3 trial had blood clots in the brain, resulting in cerebral hemorrhage. Following the conclusion that the incident was not related to the vaccine, J&J resumed its US trial.
Read more: AstraZeneca’s The risks of vaccines prolong the pandemic
Overall, there were 14 cases of clotting and bleeding events affecting patients who received J & J’s vaccine, according to a report to the FDA. There were ten in the group who received the placebo. Weitz, the McMaster professor, says so rarely that it occurs only once from thousands to millions of patients.
– With the help of Stephanie Baker, Riley Griffin and Natalie Lung
(Updates with CanSino comment in the seventh paragraph)