mRNA gene therapy (it's not a vaccine) has in fact been studied for decades. But
importantly, it has also never made it out of the early testing phase for ANY purpose, and has never been approved by any regulatory agency anywhere in the world for use in humans. You are participating in a mass human trial by taking the gene therapy masquerading as a vaccine.
None of these new COVID-19 gene therapy treatments have been approved for use in humans. They are being rolled out to the masses under Emergency Use Authorization, which literally means that these new, experimental treatments get to bypass all the safety and efficacy standards they would normally have to go through. Oh yeah, and if things go horribly wrong with the gene therapy, the manufacturers are immune from any and all liability.
When asked point blank, drug company executives admit they have no idea if the vaccine will cause lower fertility or infertility in women, have no idea if it will cause a prion disease, no idea of ANY medium or long-term side effects, etc. And of course this is to combat an illness that has a 99.99% survival rate for everyone that isn't old and dying already, fat as fuck, or immunocompromised. And remember, there's no excess mortality, the seasonal flu "miraculously disappeared" in 2020, and the people who die of COVID would die of any run-of-the-mill upper respiratory illness anyways. Take the vaccine if you want, but understand you're volunteering to be a Guinea pig for a totally untested gene therapy that won't even stop you from contracting or spreading COVID-19.