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Vaccine-induced blood clots and "VIPIT"

Posted: Tue Mar 23, 2021 10:14 am
by guy153
Reports of a theory explaining what's going on here:

https://idw-online.de/en/news765335

For some background what happens in "heparin induced thrombocytopaenia" is you give someone some heparin. It gets gummed up with a signalling protein used by platelets called PF4. In some cases the immune system decides to attack these blobs of heparin+PF4 and creates antibodies.

The "back" end of an IgG antibody binds to an Fc receptor. This isn't the antigen-specific end (that recognizes viruses and things and sticks to them). It's the other end. Platelets also have Fc receptors as it happens (I don't think anything to do with the immune system, they just use it to do platelet stuff). The antibodies bind to those Fc receptors and this activates the platelets who start causing blood clots as that is basically their job.

Since the platelets are now covered in antibodies other immune cells come along and eat them and this is what causes the very low platelet count ("thrombocytopaenia"). So this is why it paradoxically causes both low platelets and clotting. In extreme cases the treatment is to amputate your spleen since the immune cells that destroy the platelets hang out there.

It took several decades to figure all this out for heparin. But the vaccine issue looks very similar.

Anyway, with "vaccine induced prothrombotic immune thrombocytopaenia" (or "VIPIT")there's no heparin involved (unless you were already on heparin which probably makes it worse). The common factor is the IgG antibodies. Whether they are targetted at the spike proteins, the adenovirus vector, or at some other non-foreign antigen that the immune system, stimulated by the vaccine, has decided to attack, isn't clear.

But from this point it's the same-- IgG binds to platelets and causes them to both go nuts and get eaten by immune cells.

I don't think this is specific to AZ but it may be more frequent with AZ. This is the news report about a case in Florida after the Pfizer vaccine:

https://www.nytimes.com/2021/01/12/heal ... death.html

Which they're downplaying but it sounds like it was the same thing.

Re: Vaccine-induced blood clots and "VIPIT"

Posted: Tue Mar 23, 2021 11:41 am
by Splatt
Some more detail is here on specific cases:

https://www.sciencemag.org/news/2021/03 ... s-covid-19

Rare yes but i wouldn't completely rule out an issue. Seems to be affecting younger people if at all. We may not have seen it much in the UK as we generally aren't vaccinating younger people yet and those that did, most had Pfizer due to their place of work etc.

EMA in its safety report did qualify it with:
however, the vaccine may be associated with very rare cases of blood clots associated with thrombocytopenia, i.e. low levels of blood platelets (elements in the blood that help it to clot) with or without bleeding, including rare cases of clots in the vessels draining blood from the brain (CVST).
MHRA issued a side effect bulletin update for people to report prolonged bruising and headaches as well yesterday.

On top of this today is NIAID pretty much accusing AZ of misleading in their US trials by using old data:
https://www.nih.gov/news-events/news-re ... ca-vaccine

Re: Vaccine-induced blood clots and "VIPIT"

Posted: Tue Mar 23, 2021 12:05 pm
by jmc
Thrombocytopaenia was a fairly common problem with SARs CoV 1 in 2003.

https://pubmed.ncbi.nlm.nih.gov/16019455/

https://pubmed.ncbi.nlm.nih.gov/15254784/

etc..

So hardly surprising that something that triggers an immune system response equivalent to an active SARs CoV 2 infection might give rise to thrombocytopaenia.

The human immune system is about as stable as a Mexican bar on a Friday night full of armed drunk narcotraficantes. Does nt take much to get the shooting started and once started difficult to stop. In this case the blood platelets are just innocent bystanders. Collateral damage.

Re: Vaccine-induced blood clots and "VIPIT"

Posted: Tue Mar 23, 2021 5:55 pm
by guy153
jmc wrote: Tue Mar 23, 2021 12:05 pm Thrombocytopaenia was a fairly common problem with SARs CoV 1 in 2003.

https://pubmed.ncbi.nlm.nih.gov/16019455/

https://pubmed.ncbi.nlm.nih.gov/15254784/

etc..

So hardly surprising that something that triggers an immune system response equivalent to an active SARs CoV 2 infection might give rise to thrombocytopaenia.

The human immune system is about as stable as a Mexican bar on a Friday night full of armed drunk narcotraficantes. Does nt take much to get the shooting started and once started difficult to stop. In this case the blood platelets are just innocent bystanders. Collateral damage.
Good analogy :)

Covid-19 also causes blood clots and I've seen all sorts of theories about why-- e..g infection of blood vessels themselves or downregulation of ACE2 leading to oxidative stress and too much von Willebrand factor. But a similar process to this VIPIT thing sounds very plausible (and the 'V' is supposed to stand for 'Vaccine/Virus').