A comparison of the serious adverse effects of the AstraZeneca vaccine and the Pfizer-BioNTech vaccine


With the AstraZeneca vaccine there would be one case of thrombosis for every 9 thousand vaccinated. The frequency is greater than that indicated so far, equal to 1 case per 100 thousand, because the data considered are different. The study of the University of Perugia

(photo: Paul McManus via Pixabay)

After the very rare cases of thrombosis after vaccination with the vaccine Vaxzevria by AstraZeneca, to see even more clearly, a research group from the University of Perugia requested and analyzed updated data, provided by theEuropean Medicines Agency (Ema), on adverse effects. The researchers compared the post-vaccine reactions of AstraZeneca with those of the vaccine Pfizer-BioNTech: in general, according to what was reported, it emerges that Vaxzevria would be associated with a much greater number of serious and non-serious effects. In addition, the serious events associated with thrombocytopenia and venous thrombus concern 1 case su 9mila. I results are published in the journal Autoimmunity.

More cases with AstraZeneca

Researchers assessed the frequency of serious adverse events, related to thrombocytopenia, bleeding and thrombi, documented in the European database Eudravigilance of the Ema until April 16, 2021. The vaccines considered are Vaxzevria di AstraZeneca (Ae) e BNT162b2 (Bnt) di Pfizer-BioNTech, while the vaccine developed by Johnson & Johnson’s Janssen is still under investigation. “The administration of ChA [Vaxzevria ndr] has been associated with a much higher frequency of severe adverse events, the text of the publication reads, “In each reaction group Ae compared to what was found for the Bnt vaccine”. In fact, the authors considered 19 groups – or categories – of reactions associated with vaccines, divided according to the organs affected. The possible causes of this mechanism are still being studied. The authors indicate that the node may lie in the manner and quantity with which Vaxzevria produces the proteina spike del coronavirus.

How many cases

Taking for example the cases of thrombocytopenia, thrombus and hemorrhages are detected 33 episodes out of a million vaccinated with Pfizer-BioNTech e 151 always on a million with AstraZeneca. In general, the authors write, the frequency of these serious events is higher with Vaxzevria, while it is in line with that relating to the general population (how many events would normally occur, even without vaccination) in the case of Pfizer-BioNTech. In the case of the AstraZeneca vaccine the frequency is approximately one case out of 9 thousand vaccinated. Serious adverse effects related to cerebral or splanchnic venous thrombosis and / or thrombocytopenia, the authors explain, are more frequent in young people aged between 18 and 24 years and in women of childbearing age, with an incidence of 0.5 cases every 10 thousand doses.

And that’s not all. Research shows that serious adverse events from Pfizer-BioNTech’s vaccine are even lower than expected and predicted. This observation, the authors explain, suggests that the adverse effects of Covid vaccines could be underestimated and that those associated with Vaxzevria could be even 2-4 times greater of those listed above.

If the accounts don’t add up

Our data regarding thrombocytopenia and thrombus disagree with those reported by the EMA, equal to one case per 100 thousand doses “, it always reads on Autoimmunity. But how can this discrepancy be explained? The topic is certainly complex and very technical, but in general the researchers from Perugia have considered a broader picture of pathologies. What they read is that they did not consider thrombosis Cvt / Svt only if in the presence of thrombocytopenia, as has happened so far by Ema. Instead, they included cases of thrombosis both in the presence and in the absence of thrombocytopenia and also thrombocytopenia alone.

The study also speculates that the number of adverse effects caused by the AstraZeneca vaccine is similar to that of the AstraZeneca vaccine. Johnson & Johnson, but this is an aspect that is still being studied and to be demonstrated.


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