“These may not be all the possible side effects of the vaccine. Serious and unexpected side effects may occur. The possible side effects of the vaccine are still being studied in clinical trials”
So
We are the clinical trials
The published trials have been very limited, still incomplete, and problems glossed over in all the published information I have been able to find. (And all written by the manufacturers of the vaccines, who of course, are making enormous profits for their vaccines.)
Compound that with the fact that the mRNA vaccines only address the "spike protein" component of Covid-19, and NOT the rest of the virus, which quickly evolved into new variants, which may not depend on the spike protein at all.
And worst of all,the spike protein produced deliberately by the mRNA vaccines may in fact have long term negative effects on the human immune system at least as severe as produced by Covid-19.
It's too early to tell just how serious long term effects are. Here's just one example:
https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/myocarditis.html
Bkmk
But most definitely NOT ‘being studied’ !