A recent article in the BMJ describes a population based cohort study that assessed rates of cardiovascular and haemostatic events in the first 28 days after vaccination with the Oxford-AstraZeneca vaccine ChAdOx1-S in Denmark and Norway, and compared them with rates observed in the general populations.
The researchers observed increased rates of venous thromboembolic events, including cerebral venous thrombosis, among recipients of ChAdOx1-S. For the remaining safety outcomes, the researchers observed slightly higher rates of thrombocytopenia/coagulation disorders and bleeding, which could be influenced by increased surveillance of vaccine recipients. The absolute risks of venous thromboembolic events were, however, small, and the findings should be interpreted in the light of the proven beneficial effects of the vaccine, the context of any given country, and the limitations to the generalisability of the study findings.