With input from Dr Monica Vasudev

1. The risk of developing cerebral venous thrombosis (CVT) from COVID-19 appears to be several times higher than that from administration of the AstraZeneca/Oxford or the Pfizer and Moderna mRNA vaccines.
2. A University of Oxford study has noted that from a dataset of more than 500,000 COVID-19 patients, CVT would have developed in 39 per million individuals.
3. CVT has been reported in about 5 per million people after a first dose of the AstraZeneca vaccine.
4. Among more than 480,000 people administered either the Pfizer/BioNTech or Moderna mRNA vaccines, CVT was noted in 4 per million.
5. Compared to the mRNA vaccines, the risk of CVT from COVID-19 was nearly 10 times higher.
6. In comparison with the Oxford vaccine, the risk of CVT from COVID-19 was around 8-fold higher.
7. A similar pattern has been observed for portal vein thrombosis (PVT), which was observed in 436.4 per million individuals who had contracted COVID-19. In comparison, the figure was 44.9 per million for the mRNA vaccine, and 1.6 per million for those administered the AstraZeneca vaccine.
8. Major issue - the comparison showing the higher risk after COVID-19 does not exclude the possibility that the pathogenesis is the same and some common denominator should therefore be explored.
9. If the mechanism is same, it can be speculated that the high occurrence in COVID-19 compared to vaccination is because the whole virus is more thrombogenic than the spike protein alone.
10. These studies are important but they focus on showing the minor risk of vaccination instead of trying to explain the cause of complications, making use of the similarities of the events in the two populations. [Medscape]

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA