Rare cases of clotting seen with two Covid-19 vaccines have cast the spotlight on an unusual reaction that occurs when the body unleashes its immune system. firepower against platelets.
Health officials are investigating whether and how the immune response may occur in people who have received vaccines made by cancer AstraZeneca Plc and Johnson & Johnson. Concerns have grown so great that the U.S. Centers for Disease Control and Prevention and Food and Drug Administration have jointly recommended that use of the J&J vaccine be discontinued on Tuesday.
The syndrome is highly uncommon in that it is associated with increased coagulation along with a low platelet count, the blood component primarily responsible for clotting, and has only been observed in low percentages in vaccine recipients. There is pressure on governments to accelerate the immunization of millions of people in the coming months to understand the risk and avoid panic.
“The more challenging issue is how we establish responsible, right 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 we don’t frighten people out of proportion. In order of magnitude, the problem is Covid. “
Adenovirus Link
The occurrence of serious, hard-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. It raises the possibility that some of the vaccines that have been expected to deliver worldwide delivery could face significant restrictions that could limit their use, as is already happening 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 injection and one from China CanSino Biologics Inc. can also be scrutinized.
CanSino said it uses a different type of adenovirus vector than Astra or J&J. There have been no reports of serious cases of blood clotting among the 1 million people who have received the shot, the company said in a Hong Kong grant application.
Read more: blood clots, Anaphylaxis and other vaccination fears
Six women, ages 18 to 48, suffered a type of blood clot in the brain called cerebral sinus vein thrombosis after receiving the J&J vaccine, health officials said Tuesday, with one woman dead and another in critical condition. The patients all had low platelet counts, a suspicious resemblance to a complication seen 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. Although the anticoagulant is normally used to prevent blood clots, in rare cases it will turn the immune system against a platelet protein, leading to a dangerous drop in 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 very low at 1 per million, vsAstraZeneca is 1 in 100,000. The US has more than enough doses of Pfizer-BioNTech and Moderna to cover the adult population by July. But the rest of the world will face reopening economies vsUsing vaccines with rare side effects. “
– Sam Fazeli, senior pharmaceutical analyst at BIClick here to read the research.
Both the Astra and J&J vaccines “likely induce platelet antibodies,” which in rare cases lead to activation of the platelets and cerebral blood clots, says Peter Jay Hotez, an immunization expert at Baylor College of Medicine in Houston.
“Each county will have to make decisions about whether to continue” use of the vaccines, or decide on restrictions on their use, he said. “This is a problem for Africa and Latin America” as those countries relied heavily on adenovirus vaccines for their rollout.
Heparin care
People who have the vaccine reaction probably shouldn’t receive heparin, he said Jeff Weitz, a professor at McMaster University and president of the International Society on Thrombosis and Hemostasis. Other options such as Eliquis from Bristol-Myers Squibb Co. or J & J’s Xarelto are likely safer oral medications, he said.
The pause on the J&J vaccine gives CDC and FDA time to review the situation and make sure doctors who see clotting syndrome know how to respond, said Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research. The events were seen between 6 and 13 days after vaccination and were identified by the FDA through a government-run vaccine adverse reaction reporting system, Marks said in a webinar sponsored by the American Medical Association.
“Everyone knew it could be a blow to confidence in the vaccine,” he said. While the cases “could just be a statistical bias,” health authorities tried to exercise great caution.
Safety concerns have emerged with other Covid vaccines that clinicians have learned to handle, he said. For example, after several cases of anaphylaxis, a severe allergic reaction, were linked to mRNA vaccines, health authorities educated doctors about treatment.
Read more: US Calls for Cessation of J&J Shot on Clots, Roiling Unroll
Researchers think the blood clots could be caused by a rare autoimmune reaction to the vaccine that leads to an unusually low platelet count and serious blood clots. Just as heparin can in rare cases sensitize the immune system to platelets, the vaccines can cause a similar reaction.
The blood clots associated with the vaccine are ‘super rare’ and show a very unusual clotting pattern in the head or abdomen, said Mark Crowther, a haematologist and chairman of the medical department at McMaster.
Unlike a stroke, which blocks arteries that bring blood to the brain, with the vaccine-associated clots, the veins that drain blood from the head are blocked, said Crowther, who is also an officer of the American Society of Hematology. . That’s one reason patients often report severe headaches, he said.
In two studies published April 9 in the New England Journal of Medicine, a research team in Norway and another group in Germany and Austria found that patients with severe clotting reactions to the AstraZeneca vaccine had antibodies to an important clotting protein called platelet factor 4 .
New phenomenon
Six of the 11 cases of blood clotting reported by the German and Austrian researchers were fatal, while three out of five people with blood clots studied by the 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,” concluded Norwegian researchers at Oslo University Hospital.
Hints of a link to clotting may have emerged during J & J’s latest tests. In a report to the FDA, J&J said a 25-year-old male volunteer in the phase 3 study had contracted blood clotting in the brain, resulting in cerebral haemorrhage. After concluding that the event was unrelated to the vaccine, J&J resumed its US trial.
Read more: AstraZenecas Vaccine Drama Risks Prolonging the Pandemic
In total, there were 14 cases of clotting and bleeding events that received the J&J vaccine in the trial, according to a report to the FDA. There were 10 in the group that received the placebo. Events so rare that they occur only once in the thousands to millions of patients are very difficult to link to a specific cause, said Weitz, the McMaster professor.
– Assisted by Stephanie Baker, Riley Griffin and Natalie Lung
Updates with CanSino note in the seventh paragraph