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Blood clots in brain, abdomen linked to AstraZeneca COVID vaccine: NEJM
According to recent research published in the New England Journal of Medicine, an unusual blood clotting disorder has been noticed in patients after receiving their first dose of the AstraZeneca/Oxford COVID-19 vaccine.
Several cases of unusual thrombotic events and thrombocytopenia have developed after vaccination with the recombinant adenoviral vector encoding the spike protein antigen of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (ChAdOx1 nCov-19, AstraZeneca). More data were needed on the pathogenesis of this unusual clotting disorder.
Hence, Andreas Greinacher and colleagues conducted the present study where they assessed the clinical and laboratory features of 11 patients in Germany and Austria in whom thrombosis or thrombocytopenia had developed after vaccination with ChAdOx1 nCov-19.
The authors used a standard enzyme-linked immunosorbent assay to detect platelet factor 4 (PF4)–heparin antibodies and a modified (PF4-enhanced) platelet-activation test to detect platelet-activating antibodies under various reaction conditions.
Included in this testing were samples from patients who had blood samples referred for investigation of vaccine-associated thrombotic events, with 28 testing positive on a screening PF4–heparin immunoassay.
The results seen were -
a. Of the 11 original patients, 9 were women, with a median age of 36 years (range, 22 to 49). b. Beginning 5 to 16 days after vaccination, the patients presented with one or more thrombotic events, with the exception of 1 patient, who presented with fatal intracranial hemorrhage.
c. Of the patients with one or more thrombotic events, 9 had cerebral venous thrombosis, 3 had splanchnic-vein thrombosis, 3 had pulmonary embolism, and 4 had other thromboses; of these patients, 6 died.
d. Five patients had disseminated intravascular coagulation.
e. None of the patients had received heparin before symptom onset.
f. All 28 patients who tested positive for antibodies against PF4–heparin tested positive on the platelet-activation assay in the presence of PF4 independent of heparin.
g. Platelet activation was inhibited by high levels of heparin, Fc receptor–blocking monoclonal antibody, and immune globulin (10 mg per milliliter).
h. Additional studies with PF4 or PF4–heparin affinity purified antibodies in 2 patients confirmed PF4-dependent platelet activation.
Therefore, it was concluded that "Vaccination with ChAdOx1 nCov-19 can result in the rare development of immune thrombotic thrombocytopenia mediated by platelet-activating antibodies against PF4, which clinically mimics autoimmune heparin-induced thrombocytopenia."
BDS, MDS( Pedodontics and Preventive Dentistry)
Dr. Nandita Mohan is a practicing pediatric dentist with more than 5 years of clinical work experience. Along with this, she is equally interested in keeping herself up to date about the latest developments in the field of medicine and dentistry which is the driving force for her to be in association with Medical Dialogues. She also has her name attached with many publications; both national and international. She has pursued her BDS from Rajiv Gandhi University of Health Sciences, Bangalore and later went to enter her dream specialty (MDS) in the Department of Pedodontics and Preventive Dentistry from Pt. B.D. Sharma University of Health Sciences. Through all the years of experience, her core interest in learning something new has never stopped. She can be contacted at editorial@medicaldialogues.in. Contact no. 011-43720751
Dr Kamal Kant Kohli-MBBS, DTCD- a chest specialist with more than 30 years of practice and a flair for writing clinical articles, Dr Kamal Kant Kohli joined Medical Dialogues as a Chief Editor of Medical News. Besides writing articles, as an editor, he proofreads and verifies all the medical content published on Medical Dialogues including those coming from journals, studies,medical conferences,guidelines etc. Email: drkohli@medicaldialogues.in. Contact no. 011-43720751