The rare cases of coagulation that have been observed with two Covid-19 vaccines have brought to the fore an unusual reaction that occurs when the body unleashes its immunity. firepower against platelets in the blood.
Health officials are exploring whether and how the immune response can occur in people who have received vaccines given by AstraZeneca Plc and Johnson & Johnson. Concerns have grown so much 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 extremely unusual in that it involves increased clotting, along with low platelet levels, the blood component primarily responsible for clotting and has been observed only at low rates in vaccinated patients. The pressure is for governments that want to speed up the immunization of millions of people in the next few months to understand the risk and avoid panic.
“The more challenging issue is how we can make responsible and fair communication with 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 you don’t scare people too much. In order of magnitude, the problem is Covid. ”
Adenovirus Link
The occurrence of severe blood clotting events, difficult to predict in two top vaccines is an obstacle in the race to vaccinate as many people as possible before next winter. This raises the possibility that some vaccines that were relied on for global supply may have significant restrictions that could limit their use, as is already the case with the AstraZeneca vaccine in Europe.
Astra and J&J vaccines both use an adenovirus to help the immune system identify and fight the coronavirus. Other similar vaccines, the Russian shot Sputnik V and one from China CanSino Biologics Inc. may also be subject to control.
CanSino said it uses a different type of adenovirus vector than Astra or J&J. No serious cases of blood clotting have been reported among the 1 million people who received the shot, the company said in a Hong Kong stock exchange.
Read more: blood clots, Anaphylaxis and other vaccine concerns
Six women between the ages of 18 and 48 suffered 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 critical condition. All patients had low blood platelet counts, a suspicious resemblance to a complication observed with the AstraZeneca vaccine, and University of Oxford.
It is also similar to another rare coagulation disorder that occurs in people treated with heparin. While the anticoagulant is normally used to prevent blood clots from forming, in rare cases, it will turn the immune system against a platelet protein, leading to dangerous levels of reduction and substantial 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, vs.. AstraZeneca’s 1 in 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 will have savings that will reopen vs.. using vaccines with rare side effects. ”
– Sam Fazeli, senior pharmaceutical analyst at BIClick here to read the research.
Both Astra and J&J vaccines “probably induce platelet antibodies,” leading to the activation of platelets and cerebral blood clots in rare cases, says Peter Jay Hotez, an immunization expert at Baylor College of Medicine in Houston.
“Each county will have to make decisions about continuing” the use of vaccines or setting restrictions on their use, he said. “This is a problem for Africa and Latin America,” because these countries relied heavily on adenovirus vaccines for their release.
Heparin concern
People who get the vaccine should probably not receive heparin, he said Jeff Weitz, professor at McMaster University and president of the International Society of Thrombosis and Hemostasis. Other options such as Bristol-Myers Squibb Co.’s Eliquis or J & J’s Xarelto are probably safer oral medications, he said.
The break for the J&J vaccine will give the CDC and the FDA time to review the situation and make sure doctors who see coagulation syndrome know how to respond, he said. Peter Marks, director of the FDA Center for Biological Assessment and Research. The events were seen 6 to 13 days after vaccination and were identified by the FDA through a government-administered adverse event reporting system, Marks said in a webinar sponsored by the American Medical Association.
“Everyone knew it could have an impact on vaccine confidence,” he said. Although the cases “could only be a statistical aberration”, the health authorities tried to be extremely cautious.
There have been safety issues with other Covid vaccines that clinicians have learned to deal with, he said. For example, after a number of cases of anaphylaxis, a severe allergic reaction, were related to mRNA vaccines, health authorities educated doctors about the treatment.
Read more: US calls for a break from J&J shot on clots, roiling Roll
Researchers believe that blood clots can be caused by a rare autoimmune reaction against the vaccine that leads to unusual low platelets and severe clots. Just as heparin can, in rare cases, sensitize the immune system against platelets, vaccines can create a similar reaction.
Vaccine-associated blood clots are “very rare” and occur with very unusual patterns of clotting in the head or abdomen, he said. Mark Crowther, hematologist and chair of the McMaster Department of Medicine.
Unlike a stroke, in which the arteries that carry blood to the brain are blocked, with the clots associated with the vaccine, the veins that drain blood from the head become blocked, said Crowther, who is also an officer with the American Society of Hematology. This is one reason why patients often report severe headaches, he said.
In two studies published on April 9 in the New England Journal of Medicine, a team of researchers from Norway and another group from Germany and Austria found that patients who had severe clotting reactions to the AstraZeneca vaccine had antibodies to an important protein. coagulation called platelet factor 4.
The new phenomenon
Six of the 11 cases of blood clotting reported by German and Austrian researchers were fatal, while three of the five people with blood clots studied by Norwegian scientists died, according to studies by the New England Journal of Medicine.
The blood clotting disorder “is a new phenomenon, with devastating effects for healthy young adults,” concluded Norwegian researchers at Oslo University Hospital.
Coagulation clues may have appeared during J & J’s final tests. In a report to the FDA, J&J said a 25-year-old volunteer in the phase 3 study suffered blood clotting in the brain, resulting in cerebral hemorrhage. After concluding that the event was not related to the vaccine, J&J resumed its study in the USA.
Read more: AstraZeneca’s The dramatic risks of vaccines that prolong the pandemic
Overall, there were 14 cases of coagulation and bleeding in patients who received the J&J vaccine in the study, according to an FDA report. There were 10 in the placebo group. Events so rare that they occur once in only thousands to millions of patients are very difficult to relate to a specific cause, said Weitz, Professor McMaster.
– With the assistance of Stephanie Baker, Riley Griffin and Natalie Lung
(Updates with CanSino comment in the seventh paragraph)