The previous vaccines actually kept you from coming down with the illness they were created to stop. In addition they did not have serious side effects like myocarditis and even death. The few times vaccines had serious side effects they were immediately taken off the market.
This new MRNA vaccine infects your immune cells with Messenger RNA, causing them to create a spike protein. Never before has the human body made a virus spike protein. This is highly experimental. How does your body know when to stop making spike proteins? And can it be re-triggered in the future to create more spike proteins? What are the medical ramifications of that?