Thread by @CzypionkaThomas

Why the current adverse effects concerning #AstraZeneca are problematic for the fight against the #pandemic (thread):

For the ones not familiar with these rather complicated medical facts, an introduction first:
We need to distinguish between the thromboembolism due to

deep vein thrombosis (DVT) issue and the cerebral venous sinus thrombosis (CVST) WITH thrombocytopenia issue.

In an observed vs expected analysis, the former does not seem to be out of the ordinary. But the CVST plus thrombocytopenia is, as one case is to be expected in the

roughly 1.6 mio vaccinated in Germany and seven cases have been observed (actually, six CVST and one patient with primarily cerebral hemorrhage).
It is important to note that the matter at hand is CVST plus thrombocytopenia, as the pathomechanism is completely different

from deep vein thrombosis. Such a constellation is normally observed in the course of heparin therapy. More precisely, under heparin therapy there is the adverse effect called HIT II (heparin induced thrombocytopenia type 2).

It is caused because in some people, antibodies against the complex of heparin and a protein called platelet factor 4 (PF4) are formed. As heparin is a large molecule, several such IgG can then bind to it and with their constant domain bind thrombocytes (or platelets).

This package of heparin-bound thrombocytes is then eliminated in the spleen. And in some people, this phenomenon does not only cause thrombocyte levels to drop but to make them clot in the cerebral sinuses.

This also explains why the one case that does not really have CVST is counted toward the seven cases.

But in the vaccine there is no heparin. However, a HIT II like syndrome has been described without heparin, i.e. spontaneous: tandfonline.com/doi/abs/10.310…

So it may well be that a part of the vaccine acts similarly, as the main pathomechanism behind the antibody formation is the anionic property of heparin, binding the strongly cationic PF4. I think it is not likely that the market authorisation will be revoked due to this.

Unless things change dramatically, it remains a rare adverse effect. But from a public health view, this is a major problem, as the image of AZ vaccine is not only further damaged, but many people and media will also not distinguish between the two issues.

Now there is the impression that the initial reports about DVT/embolisms were actually a first warning sign that was dismissed. And there is a rare risk that getting vaccinated can actually be lethal.

Now people tend to overweight small risks. This will severely hamper vaccine uptake and is a setback in the fight against the pandemic.