This is how a vaccine works.
A vaccine works by training the immune system to recognize and combat pathogens, either viruses or bacteria. To do this, certain molecules from the pathogen must be introduced into the body to trigger an immune response. These molecules are called antigens, and they are present on all viruses and bacteria.
So to work we have to inject some variant of covid to train our immune system to respond to the real thing. You don’t have to ask why every pharmaceutical company working in this area is insisting on financial immunity from prosecution if something goes wrong on a grand scale.