Two Scandinavian countries that halted the use of the Oxford vaccine suffered 11 excess events for every 100,000 vaccinations, according to a new analysis of the thrombotic risks associated with the programme, published today.
The analysis, in The BMJ, confirms the rarity and nature of the events – but experts say it is still hard to compare the vaccine risks with the risks of unfettered spread of COVID-19.
According to one expert, without vaccination, the population would face significantly increased risks of thrombotic events from viral infection.
The study in Norway and Denmark found 59 venous thrombotic events compared with 30 that would have been expected. There was no additional risk of arterial thrombosis.
There were 2.5 incidents of cerebral venous thrombosis for every 100,000 vaccinations. Other events included thrombocytopenia and incidents of bleeding and clotting disorders – which, the researchers say, might have simply been highlighted by increased surveillance.
The researchers, led by Professor Anton Pottegård, a public health specialist at the University of Southern Denmark, Odense, Denmark, write: “The absolute risks of venous thromboembolic events described in this study are small, and the findings should be interpreted in the context of the benefits of covid-19 vaccination at both the societal and the individual level.”
Writing in the journal, Professor Paul Hunter, of the University of East Anglia, UK, says the findings support the conclusions of UK and EU regulators that the benefits of the vaccine outweigh its risks for most age groups.
He writes: “Those countries that delayed their own vaccination programmes at a time of high transmission rates by declining to use available Oxford-AstraZeneca vaccines should know that their decision will have contributed to an increase in the number of avoidable deaths from covid-19.”
And the BMJ editors Rafael Perera and John Fletcher write: “The choice we nearly all face is between eventual SARS CoV2 infection or vaccination. The Astra-Zeneca vaccine is clearly a good choice, despite the likely risks reported in this study. Quantifying the comparative risk associated with other vaccines is now a research (and public health) priority.”
Arterial events, venous thromboembolism, thrombocytopenia, and bleeding after vaccination with Oxford-AstraZeneca ChAdOx1 in Denmark and Norway: population based cohort study. BMJ 6 May 2021
Leave a Reply