The paper published in the New England Journal of Medicine said no new cases of vaccine-induced immune thrombocytopenia and thrombosis (VITT) have been observed in the UK since it was decided to give this vaccine only to people aged 40 or older. Other countries have also put age restrictions on the shot.

According to the study, around 85% of those who suffered rare blood clots after receiving the vaccine now known as Vaxzevria were aged under 60, even though more doses altogether were administered to older people. In those under 50, incidence was around 1 in 50,000, in line with expectations. The British experts said the study reinforced prior understanding of the risk-benefit calculation of vaccination.

Sue Pavord, a consultant hematologist at Oxford University Hospitals who led the research, said the clotting for the most part affected young people who were otherwise healthy. The condition was especially dangerous if it resulted in bleeding in the brain.

The condition had an overall mortality rate of 23%, but this rose to 73% in cases with cerebral venous sinus thrombosis (CVST), the researchers said, although treatments like blood plasma exchange increased the survival rate for severe cases to 90%.

Of the 294 possible cases analyzed, the study found 220 to be definite or possible cases of VITT. All the incidents were observed solely in people receiving the AstraZeneca dose. Multiple clots were found in about a third of cases, and almost all those hospitalized experienced the condition between five to 30 days after a first dose of this vaccine.

Author: Dede Williams, Freelance Journalist