The risk of death from the rare clotting syndrome associated with AstraZeneca’s COVID-19 vaccine is highest among patients with severely low platelet count and intracranial haemorrhage, UK researchers have found.

And in 50% of those who develop thrombosis with thrombocytopenia syndrome (TTS), the most common thrombotic site at presentation was the cerebral veins, according to analysis of the first 220 cases reported in the UK.

The prospective study on TTS – also known as vaccine-induced immune thrombocytopenia with thrombosis (VITT) – showed the overall mortality rate was 22% but jumped to 73% for patients with severely depleted platelets and intracranial haemorrhage.

Lead author Dr Sue Pavord said the overall risk of TTS following the AstraZeneca vaccine was very rare but the consequences “can be devastating”.