Thrombosis after the vaccine and covid
The risk of thrombosis from covid was higher compared to vaccines
Vyacheslav Gomenyuk, N+1
The risk of developing thrombosis of the cerebral veins and portal vein in covid significantly exceeds the similar risk when vaccinated against covid with RNA vaccines. As reported in the preprint of the article on the website osf.io scientists came to this conclusion as a result of analyzing more than a million electronic medical records of patients who had covid or flu, or received a vaccine from covid. According to their preliminary calculations, the risk of developing thrombotic complications after COVID-19 is about eight times higher compared to conditions after vaccination.
In the spring of 2021, scientists from different countries began to report that within two weeks after the introduction of the anti-coronavirus vaccine from AstraZeneca, people developed thrombocytopenia (a decrease in the number of platelets in the blood), which was accompanied by thrombosis. Because of this, some countries have suspended the use of this vaccine. Despite the fact that the European Medicines Agency has recognized thrombosis as a very rare side effect of the vaccine, and other scientists have already managed to explain the cause of these thrombosis after vaccination, the topic of thrombotic complications after anticoronavirus vaccinations does not cease to be relevant.
Moderna and Maxime Taquet from Oxford University studied electronic records of patients with covid and influenza and people who were vaccinated with Pfizer/BioNTech or Moderna RNA vaccines. Scientists were interested in the frequency of occurrence of thrombosis of the veins of the brain and portal vein in all three conditions, and with covid and influenza, cases of thrombosis were included in the analysis if they occurred within two weeks of diagnosis. The search for diagnoses was carried out according to the codes of the International Classification of Diseases of the tenth revision.
The group of covid patients included 513284 patients. Slightly more than half of them were female, and their average age was 46.6 years. Of all covid patients, 20 were diagnosed with cerebral vein thrombosis (absolute risk 39.0 per million people). At the same time, the risk was significantly higher among patients with cardiovascular diseases, for example, narrowing or blockage of the cerebral and precerebral arteries and intracranial hemorrhages. Six cases were observed in patients under the age of 30, four — between 30 and 39 years, two — between 40 and 49 years, two — between 50 and 59 years, three — between 60 and 69 years, and three — between 70 and 79 years. Three patients had varicose veins before the diagnosis of COVID-19.
Compared with influenza, the risk of cerebral vein thrombosis was significantly higher (p=0.003) after COVID-19. In the influenza group (172742 patients), the absolute risk of thrombosis was 0.0 per million people (confidence interval 0.0–22.2). In the vaccine group (489871 patients), only two cases of cerebral vein thrombosis were observed: in the first case, the patient received a Pfizer/BioNTech vaccine (a total of 331503 people received this vaccine in the study), and in the second there was no information about which vaccine the patient was vaccinated with. The average absolute risk was also lower compared to covid — 4.1 per million people (p<0.001).
In addition, the risk of developing cerebral vein thrombosis associated with covid was also higher than that currently reported by the European Medicines Agency after vaccination with AstraZeneca: currently 169 cases out of 34 million people, or 5.0 per million people. Mortality among patients with cerebral vein thrombosis within two weeks after covid was 20.0 percent (four out of 20 patients).
The same tests were performed by scientists for cases of portal vein thrombosis. The absolute incidence within two weeks after the diagnosis of COVID-19 was 436.4 per million people (224 cases of portal vein thrombosis in the group). It was significantly higher (p<0.001) than in the influenza group (98.4 per million people) and in the vaccine group (44.9 per million people p<0.001).
In the last group, 22 cases were observed. Half of BioNTech's cases occurred after vaccination with Pfizer/BioNTech, two cases after vaccination with Moderna vaccine (a total of 70939 patients), and it is unknown which vaccine the remaining nine people received. Mortality from portal vein thrombosis after covid was 18.3 percent (41 out of 224 patients).
Scientists were able to study laboratory parameters only in the covid group. Although these data do not cover the majority of patients with cerebral vein thrombosis, they show that some of these patients had significantly higher levels of D-dimer than patients with COVID-19 who did not develop thrombosis. At the same time, patients with portal vein thrombosis were prone to significantly lower levels of fibrinogen and thrombocytopenia.
Although these findings require repetition and confirmation, they highlight the risk of serious thrombotic events in COVID-19. Despite the fact that the magnitude of risk cannot be reliably quantified in this study due to its design, the risk of thrombotic complications after COVID-19 is about eight times higher compared to vaccines and about 100 times higher compared to the population level. Thus, the current data highlight the risk of serious thrombotic complications of covid and may help in the debate about the risk-benefit ratio for existing COVID-19 vaccines.
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