So they reassure you by telling you they have only been "studied before" not widely used and use it in cancer treatment, there is still no cure for cancer and many times cancer treatments are experimental.
"mRNA Vaccines Are New, But Not Unknown
Researchers have been studying and working with mRNA vaccines for decades. Interest has grown in these vaccines because they can be developed in a laboratory using readily available materials. This means the process can be standardized and scaled up, making vaccine development faster than traditional methods of making vaccines.
mRNA vaccines have been studied before for flu, Zika, rabies, and cytomegalovirus (CMV). As soon as the necessary information about the virus that causes COVID-19 was available, scientists began designing the mRNA instructions for cells to build the unique spike protein into an mRNA vaccine.
Future mRNA vaccine technology may allow for one vaccine to provide protection for multiple diseases, thus decreasing the number of shots needed for protection against common vaccine-preventable diseases.
Beyond vaccines, cancer research has used mRNA to trigger the immune system to target specific cancer cells."-CDC https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/mrna.html
I don't think the vaccine is bad, on purpose or not, it's just that with the side effects of the current vaccine it's not worth taking. I also don't like how the CDC is constantly moving the goalpost and lying to us. I have a friend who is also a microbiologist and according to him the vaccine hasn't been tested on long term effects, making it still risky on the long run, again not worth the risk for me and many others.
I guess Trump summed it up nicely; "The cure can't be worse than the disease."