The rare cases of coagulation that have been seen with two Covid-19 vaccines have put the focus on a rare reaction that occurs when the body triggers its immunity. firepower against blood platelets.
Health officials are exploring whether and how the immune response can occur in people who have received vaccines made for AstraZeneca Plc i Johnson & Johnson. Concerns have risen so much that the U.S. Centers for Disease Control and Prevention and Food and Drug Administration jointly recommended a pause in the use of the J&J vaccine on Tuesday.
The syndrome is very unusual in that it involves an increase in clotting along with low platelet levels, the blood component primarily responsible for clotting, and has only been seen at low rates in vaccine receptors. Pressure is being put on governments that want to speed up the immunization of millions of people over the next few months to understand the risk and avoid panic.
“The most challenging issue is how we can make responsible and correct 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 that we don’t disproportionately scare people. In order of magnitude, the problem is Covid. “
Adenovirus link
The onset of serious and unpredictable 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 available to supply supplies around the world could impose significant restrictions on them that could limit their use, as is already the case with the AstraZeneca vaccine in Europe.
Astra and J&J vaccines use an adenovirus to help the immune system identify and fight the coronavirus. Other similar vaccines, sputnik V from Russia 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. There have been no reports of serious cases of blood clotting among the 1 million people who have been shot, the company said in a statement from the Hong Kong Stock Exchange.
Read more: Blood clots, Anaphylaxis and other vaccine fears
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 levels of blood platelets, a suspicious resemblance to a complication seen with the AstraZeneca vaccine and the Oxford University.
It is also similar to another rare clotting disorder that occurs in people treated with heparin. Although the anticoagulant is commonly used to prevent blood clots, in rare cases it will convert the immune system against a platelet protein, leading to a dangerous reduction in levels and substantial clotting.
What Bloomberg Intelligence says:
“The CDC is doing well even though this rare blood clotting event has a very low rate of 1 per million, vs.. 1 from AstraZeneca for every 100,000. The United States has more than enough doses of Pfizer-BioNTech and Moderna to cover its adult population in July. But the rest of the world will have heavy reopening economies vs.. using vaccines with rare side effects “.
– Sam Fazeli, senior analyst of BI pharmaceuticalsClick on here to read the research.
Both the Astra and J&J vaccine “probably induce antiplatelet antibodies,” leading to activation of platelets and cerebral blood clots in exceptional cases, says Peter Jay Hotez, an immunization expert at Baylor College of Medicine in Houston.
“Each county will have to make decisions about continuing” with the use of vaccines or deciding restrictions on use, he said. “This is a problem for Africa and Latin America,” as these countries relied heavily on adenovirus vaccines for their deployment.
Concern for heparin
People who have the vaccine reaction probably should not receive heparin, he said Jeff Weitz, professor at McMaster University and president of the International Society on Thrombosis and Hemostasis. Other options like The Bristol-Myers Squibb Co. Eliquis or J&J’s Xarelto are probably safer oral medications, he said.
The pause in the J&J vaccine will give the CDC and FDA time to review the situation and make sure doctors who see the clotting syndrome know how to respond, he said. Peter Marks, director of the FDA’s Biological Products Evaluation and Research Center. The events were seen 6 to 13 days after vaccination and were identified by the FDA through a government-administered adverse event information system, Marks said at a webinar sponsored by the American Medical Association.
“Everyone knew it could cause success in vaccine confidence,” he said. While the cases “could only be a statistical aberration,” health authorities tried to be very careful.
Safety issues arose with other Covid vaccines that doctors have learned to deal with, he said. For example, after several cases of anaphylaxis, a severe allergic reaction, were related to mRNA vaccines, health authorities educated doctors about treatment.
Read more: US calls for a break in J&J’s shooting against clots, roiling Roll out
Researchers think blood clots can be caused by a rare autoimmune reaction to the vaccine that leads to an unusual number of low platelets and severe clots. Just as heparin can, in rare cases, sensitize the immune system to platelets, vaccines can create a similar reaction.
Vaccine-associated blood clots are “super rare” and appear with very unusual clotting patterns in the head or abdomen, he said. Mark Crowther, hematologist and chairman of McMaster’s medical department.
Unlike a stroke, where the arteries that carry blood to the brain are blocked, with the clots associated with the vaccine, the veins that drain the blood from the head are blocked, said Crowther, who is also an officer in the American Society of ‘Hematology. That’s one of the reasons patients often report serious headaches, he said.
In two studies published on April 9 in the New England Journal of Medicine, a research team in Norway and another group in Germany and Austria found that patients who had severe clotting reactions to the AstraZeneca vaccine had antibodies against a important clotting protein called platelet factor 4.
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 in the New England Journal of Medicine.
Norwegian researchers at Oslo University Hospital concluded that blood clotting disorder “is a new phenomenon with devastating effects for healthy young adults for the rest.”
Signs of a connection to coagulation may have emerged during the final J&J tests. In a report to the FDA, J&J said a 25-year-old male volunteer in his phase 3 trial had suffered a blood clot in his brain, causing cerebral hemorrhage. After concluding that the event had nothing to do with the vaccine, J&J resumed its trial in the US.
Read more: D’AstraZeneca The risks of the vaccine drama that prolong the pandemic
Overall, there were 14 cases of clotting and bleeding from patients who received the J&J vaccine during the trial, according to an FDA report. There were ten in the group that received the placebo. Such rare events that occur once every thousands and millions of patients are very difficult to relate to a specific cause, said Weitz, McMaster’s professor.
– With the assistance of Stephanie Baker, Riley Griffin and Natalie Lung
(Updates with CanSino’s comment in the seventh paragraph)