Thrombosis with the AstraZeneca vaccine: what consequences for the vaccination campaign in Europe?

Bad weather for AstraZeneca. The Swedish-British vaccine had been under fire for several weeks for suspected cases of thrombosis (blood clots). On Wednesday April 7, the European Medicines Agency (EMA) issued the conclusions of its investigation: blood clots must be listed as a side effect ” very rare “, but they cannot overshadow the risk / benefit balance “Positive” vaccine.

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European health ministers met in the evening by video conference. In a tweet, EU Health Commissioner Stella Kyriakides called on the Twenty-Seven to “Speak with one voice across the EU to improve public confidence” on vaccination. The appearance of thrombosis has caused the confidence of the AstraZeneca vaccine to drop considerably among Europeans.

In search of the lost trust

The change in assessment of the AEM – who until now judged the vaccine “Safe and effective” – shouldn’t help. “There is undeniable image damage, but there is always a risk with drugs”, relativizes Antoine Flahault, epidemiologist and director of the Institute of Global Health at the University of Geneva. 222 atypical thromboses were counted out of the 34 million doses injected throughout the European Economic Area (EU, Iceland, Norway, Liechtenstein) and in the United Kingdom. 18 people died from it, according to figures from the AEM.

European experts failed to determine any “Specific risk factor” like age or gender. If they note a predominance of cases in women under the age of 60, it can also be explained by the fact that health workers (predominantly female) have been widely vaccinated with AstraZeneca.

Age, vaccine imbroglio

For now, the Twenty-Seven have not agreed on a common vaccine policy. Despite calls for union, in the evening Belgium limited – like France – its injection to over 55s. Italy and Spain followed soon after and opted for the solution already put in place by Germany to reserve the AstraZeneca for over 60s.

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The surprise came from the United Kingdom, the birthplace of the AstraZeneca vaccine. Just as the AEM was delivering its findings, the British drug regulator recommended reserving the vaccine for over 30s. The country, whose vaccination campaign is one of the most advanced in the world, has massively vaccinated with AstraZeneca, but with a single dose. But like the European Union, it is now facing major delivery delays which are slowing down the campaign.

What about the second dose

Limiting his injection to a higher age group is justified, in the eyes of Antoine Flahault, given that “The benefit / risk ratio remains very favorable for people who have a very high risk of developing a serious form of the disease”. For younger people, less at risk from Covid but more prone (all things considered) to develop thrombosis, the Pfizer / BioNTech, Moderna, and soon Johnson & Johnson vaccines offer an interesting alternative.

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For people who are waiting for their second dose of AstraZeneca, the CNRS researcher at the Cochin Institute, Morgane Bomsel, deplores that no answer or decision has been given on their case. But whatever the Twenty-Seven decide, it is always possible to fall back on other vaccines, she says. “In adenovirus vaccine research, it is common to consider a different vaccination between the first injection (which stimulates the antibodies) and the booster (which refines the specificity of the antibodies). “

Messenger RNA vaccines like Pfizer / BioNTech and Moderna use technology too recent to comment on this eventuality. But the Johnson & Johnson vaccine like the Russian Sputnik V, which both work on the same principle as the AstraZeneca, seem ideal to take over if necessary.


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