European medical regulators concluded on Wednesday that there is a strong link between AstraZeneca’s COVID-19 vaccine and life-threatening conditions that include the unusual combination of blood clots and low platelet levels.
According to the European Medicines Agency, a regulatory agency of the European Union, the conditions should be listed as a “very rare side effect” of the vaccine.
The conclusion was based on the EMA’s in-depth review of 86 blood clotting events among approximately 25 million people vaccinated with the AstraZeneca vaccine in Europe and the United Kingdom. Of the 86 blood clotting events, 18 people died. Most – but not all – cases occurred in women under the age of 60.
The events reviewed by the EMA included 62 cases of cerebral venous sinus thrombosis (CVST), a rare form of stroke in which a blood clot prevents blood from draining from the brain. The remaining 24 cases had splanchnic arterial thrombosis, which includes blood clots in the veins that drain blood from the abdomen.
In addition to the 86 cases investigated, the EMA estimated that there is a reporting rate of one case of the side effect in 100,000 people vaccinated.
Curious case
Oddly enough, the coagulation events were accompanied by low levels of platelets, these are the blood cell fragments that stick together to form blood clots. Usually low platelets lead to increased bleeding, not clotting. Regulators have noted that this unusual combination looks like a condition called heparin-induced thrombocytopenia or HIT. In rare cases, patients who receive heparin – an anticoagulant – see a drop in their platelets, but go into a hypercoagulable state, which can lead to widespread clotting and death.
HIT develops as a result of an abnormal immune response. In a response to heparin that is not fully understood, the immune systems of some patients produce antibodies that attack a common platelet protein called Platelet Factor 4, or PF4. This in turn causes platelet activation and pro-clotting particles, leading to HIT.
Some researchers suspect that the blood clotting events associated with the vaccination of AstraZeneca may also lead to a similar berserk immune response – and it may be treated. Extremely preliminary data – published online but not yet evaluated in a journal or peer-reviewed – suggest that the rare condition in some vaccinees can be treated with non-heparin anticoagulants, as well as with a high dose of immunoglobulin . activation in HIT patients.
In its announcement Wednesday, the EMA noted that the recognition of the early signs of blood clots and low platelets is critical, and it can avoid serious consequences to get quickly specialized treatment.
The EMA noted that recently vaccinated people should beware of:
- short of breath
- chest pain
- swelling in your leg
- persistent abdominal pain
- neurological symptoms, including severe and persistent headache or blurred vision
- small blood stains under the skin outside the injection site
As seen in people who develop HIT after heparin, the blood clotting events and low platelet counts seen in vaccinated people usually develop within two weeks of receiving their first dose.
Although the EMA has strengthened the link between the clot and the AstraZeneca vaccine, it still recommends using the vaccine. “The reported combination of blood clots and low platelets is very rare,” the agency noted, “and the overall benefits of the vaccine to prevent COVID-19 outweigh the risks of side effects.”
AstraZeneca-drama
The conclusion follows weeks of drama surrounding the vaccine, in which more than a dozen countries that have already approved the use of the vaccine suddenly stopped vaccinations out of concern for the blood clots – and then resumed use out of concern about the spread of the vaccine. COVID-19.
Together with the EMA, the World Health Organization continues to strongly argue that the benefits of the efficacy of the AstraZeneca vaccine in preventing deadly COVID-19 infections outweigh the risks of extremely rare blood clotting conditions.
Nevertheless, Germany withdrew last week to restrict the use of the vaccine among people under 60, the age group in which most – but not all – of the rare coagulation events occurred. And on Tuesday, the University of Oxford, which co-developed the vaccine with AstraZeneca, said it had disrupted a small UK trial of the vaccine in children and teenagers.
Meanwhile, AstraZeneca is still trapped in communications bungles. In the latest bug, the company made a very unusual and worrying splash with a panel of U.S. experts who had to oversee the COVID-19 vaccine trial and data. The panel, called the Data and Safety Monitoring Board, claimed that AstraZeneca had selected the trial data it trumpeted in a press release, possibly misleading the public about the actual effectiveness of the vaccine.
The company has defended its actions, but has not yet submitted its data to the U.S. Food and Drug Administration to obtain an emergency permit. Last week, the leading expert on infectious diseases, Anthony Fauci, suggested that the US might not need the AstraZeneca vaccine, even if it was approved, because it has enough stock of the three vaccines already used in America.
Problem for Johnson & Johnson
The new side effect in the EU will make things more difficult for AstraZeneca. And it is also likely to cast a shadow over the Johnson & Johnson COVID-19 vaccine, which is authorized in the US and elsewhere and uses the same design as the AstraZeneca vaccine.
Both vaccines use an adenovirus vector. Adenoviruses are common viruses that can cause cold infections and other mild illnesses in humans. For the delivery of vaccines, they are designed so that they can not repeat in cells or cause diseases, but can deliver the genetic code of a more dangerous germ to cells. In the case of the COVID-19 vaccines, the engineered adenoviruses produce the code of the SARS-CoV-2 vein protein, which adorns the outside of the particle of the virus. The spike protein is what SARS-CoV-2 uses to invade and enter human cells – and it is an important target for powerful antibodies and other immune responses. Once the adenovirus vector provides the code for the peak, our cells can make their own versions of the protein and use it to train immune responses that will recognize and destroy the SARS-CoV-2 virus.
A potential pitfall of adenovirus-based vaccines is that adenoviruses can also bind to platelets and cause problems. Some pre-pandemic data have suggested that adenoviruses can activate platelets and lead to a low platelet count. But the connection between this and the vaccine and the mechanism that causes blood clotting in vaccines needs much more information to understand.
The side effects seen in the AstraZeneca vaccine raise concerns about Johnson & Johnson. During the clinical trials of the Johnson & Johnson vaccine, there was an early sign of an increased risk for these blood clotting conditions in vaccines, Peter Arlett, head of data analysis at the EMA, said in a press release on Wednesday. But the link was never confirmed, he added.
Of the approximately 4.5 million people who received the Johnson & Johnson vaccine worldwide, three cases of blood clotting events similar to those seen in people who received the AstraZeneca vaccine were reported, Arlett said. These numbers are ‘very small’, he emphasized. “However, it is being investigated carefully … I think it would be fair to say that there is an intensive monitoring of the problem in the vaccines.”