The many reports of deaths and serious health problems from the vaccine have found explanations in a number of reports by scientists. The reports are highly technical, but I think I can provide the gist of the explanation.
The mRNA Covid vaccines themselves use Spike. Therefore the vaccines induce similar effects to the virus, the toxicity of which stems mostly from the effects of Spike.
The virus enter cells when its Spike binds to ACE2, a protein present on many cells. Spike alone binds to ACE2 and this is toxic to endothelial cells, to cardiac pericytes and to brain pericytes. Spike binding to ACE2 on platelets leads to thrombosis and thrombocytopenia.
Rats and mice were used to test whether Spike is toxic. This was a mistake or an intended deception, because it does not bind well to ACE2 found in mice and rats. Hamsters should have been used for the test, because ACE2 from hamsters is similar to that from humans. Apparently, this was known, but rats and mice were used anyway.
It has been discovered that the virus seems preadapted to human cells. Humans are the species to which it binds best. It does not bind well at all to most species including bats. In other words, Covid is a virus engineered for humans, and the mRNA vaccines are toxic in themselves.
This information is known, but it is being kept from the public while vaccination continues to be urged.