AstraZeneca COVID Vaccine: Causal Link to Severe Thrombosis Established

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Note: The risk is still very small for most people with this vaccine, especially given that millions have received the vaccine, especially in the UK, without incident. Additionally, other COVID-19 vaccines have also been found to be associated with similar clots in rare cases (e.g., the Johnson and Johnson vaccine, and possibly Pfizer but that’s uncertain at this time) but so far this study which only looked at the AstraZeneca version, is the first to find a causal link.

It should also be noted that many other medical factors have been associated with a small risk for similar clots, including women on birth control pills or other hormone treatments, individuals with vascular disease, diabetics, and other medical conditions, not to mention smoking. People who are already carrying a risk for clots should probably advise medical personnel of this and request a different vaccine until the risks are further clarified. ~ admin

AstraZeneca COVID Vaccine: Causal Link to Severe Thrombosis Established

Sue Hughes
April 12, 2021

Two scientific studies establishing a causal relationship between the AstraZeneca COVID-19 vaccine and severe thrombotic complications have now been published.

The articles — one from a German/Austrian/Canadian collaboration and one from a Norwegian group — were published online April 9 in the New England Journal of Medicine.  

A preliminary report of the German-led study was first published as a preprint on Research Square on March 28.


Both articles reach the same conclusion — that these unusual severe thrombotic events that are accompanied by thrombocytopenia are caused by rogue antibodies directed against platelet factor 4 (PF4), which causes massive platelet aggregation and thrombosis, and results in a reduced platelet count elsewhere, leading in turn to bleeding.  Patients can therefore have both severe thrombosis and severe bleeding.

The syndrome is very similar to the well-known condition of heparin-induced thrombocytopenia (HIT) and is diagnosed and treated in the same way, with the administration of intravenous immunoglobulins (IVIG) and anticoagulants. The syndrome associated with the vaccine has been named vaccine-induced immune thrombotic thrombocytopenia (VITT).

At a press briefing on his study, lead author of the German-led paper, Andreas Greinacher, MD, head of the Institute of Immunology and Transfusion Medicine, University Hospital Greifswald, Germany, said: “There is clear evidence that there is a very close link to this severe thrombotic complication and the AstraZeneca vaccine. There is clear causality between the pathogenic antibody and the thrombotic complications, and we have found this antibody in many people who have developed these complications after the AstraZeneca vaccine.”

The German study reports a total of 28 cases of this condition, with a more detailed description of the first 11 patients, aged 22-49 years, who presented with serious thrombotic complications including cerebral venous sinus thrombosis (CVST), splanchnic vein thrombosis, disseminated intravascular coagulation (DIC), and pulmonary embolism within 5-16 days of receiving the AstraZeneca vaccine. Six patients died.  

Greinacher said they have now analyzed 40-50 cases, all of which show the presence of the PF4 antibodies. “All the cases show the same picture,” he said. “Thrombotic complications develop within a couple of weeks of having the AstraZeneca vaccine and the link between the vaccine and the occurrence of this pathogenic antibody is very strong.”

In the Norwegian study, a group led by Nina Schultz, MD, Oslo University Hospital, note that older people in Norway have been given the Pfizer vaccine, with the AstraZeneca vaccine generally being used for healthcare workers under age 65 years. As of March 20, when administration of the AstraZeneca vaccine was paused, 132,686 people in Norway had received one dose of the vaccine and none had received the second dose.




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