New Data Suggest Cause of Post-COVID Vaccine Blood Clots

Hans-Christoph Diener, MD, PhD


June 08, 2021

This transcript has been edited for clarity.

Dear colleagues, I'm Christoph Diener from the Department of Neurology at the University of Duisburg-Essen in Germany. This month, I'd like to concentrate on new data on two very important topics: cerebral venous sinus thrombosis after vaccination against COVID-19 and the treatment of epilepsy.

The Latest on a Rare Complication of COVID-19 Vaccines

At the time of this recording, about 100 cases of cerebral venous sinus thrombosis following COVID-19 infection have been described in Europe. The majority of these occurred after vaccination with the AstraZeneca vaccine. On May 1, 12 cases were reported in the United States following vaccination with the Johnson & Johnson vaccine. Both of these vaccines are vector-based.

The mechanism behind postvaccination cases of thrombosis or thrombocytopenia was elucidated by a research group in Greifswald, Germany. They found that these patients develop antibodies against platelet factor 4, which leads to thrombocytopenia and an increased risk for venous thrombosis, in particular sinus venous thrombosis. The new term for this condition is "vaccine-induced immune thrombotic thrombocytopenia."

In Germany, 62 cases of cerebrovascular events after COVID-19 vaccination were identified up until mid-April 2021. Forty-five cases of cerebral venous thrombosis were identified; 82% following AstraZeneca vaccination, 18% after Pfizer-BioNTech, and no cases after Moderna. Of these patients, 78% were females, 80% were below the age of 60, and 58% had antibodies against platelet factor 4, which highlights the underlying relationship. There were no cases of positive antibodies in patients with cerebral venous thrombosis who received the Pfizer-BioNTech vaccine.

The important news is that there is an increased risk for sinus venous thrombosis in females irrespective of age, but there is no increased risk in males. However, we must remember that the risks of a COVID-19 infection — for example, death or having severe consequences — are much higher than the risk for sinus venous thrombosis. And the risk for sinus venous thrombosis is 10 times higher in those with a COVID-19 infection compared with receiving the COVID-19 vaccine.

Therefore, I think the bottom line is, if our healthcare system has a choice, then perhaps females should be vaccinated with the Pfizer-BioNTech or Moderna vaccines, whereas in males it doesn't really matter.

Treating Newly Diagnosed Epileptic Seizures

The second piece of big news this month comes from a wonderful pragmatic study program conducted in the United Kingdom called SANAD (Standard And New Antiepileptic Drug), in which researchers compared different antiepileptic medications in patients with newly diagnosed epilepsy. Results of the first SANAD trial were published several years ago. Investigators showed that in partial epilepsy, lamotrigine is superior to carbamazepine, oxcarbazepine, gabapentin, and topiramate, whereas in generalized epilepsy, valproate was superior to lamotrigine and topiramate.

Results of the SANAD-II trials were offered in two separate publications. In the study of focal epilepsy, 990 patients were treated and observed for 2 years. Lamotrigine was found to be superior to both zonisamide and levetiracetam, primarily owing to its superior tolerability profile.

In the second study, 520 patients with newly diagnosed generalized seizures were also treated and followed for 2 years. Results showed that valproic acid was superior to levetiracetam, once again in terms of tolerability and adverse events. However, we must remember that valproic acid poses a problem in females of child-bearing potential, because the drug clearly is teratogenic.

What I really like about the SANAD studies is their pragmatic designs. They look at both efficacy as well as at adverse events that can lead to termination of a particular drug.


In conclusion, the most important neurologic data to arrive this month are about the very low risk for sinus venous thrombosis after vaccination with the AstraZeneca and Johnson & Johnson vaccines. The mechanism behind this thrombotic thrombocytopenia is obviously the development of antibodies against platelet factor 4.

Dear colleagues, I'm Hans-Christoph Diener from the University of Duisburg-Essen. Thank you very much for listening and watching.

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