I mean you're getting the mRNA in your body one way or the other. One choice is to inhale someone else's cough droplets, then the self-replicating nano-machines

I mean you're getting the mRNA in your body one way or the other. One choice is to inhale someone else's cough droplets, then the self-replicating nano-machines inside the sputum drops take over the cells in your lungs, explode them and spread out of control until your immune system catches up and kills even more of your cells by just absolutely nuking everything around them. That's "natural immunity". You could also get a shot with a precisely controlled dose of one non-functional part of the virus that your immune system can then learn to recognize and destroy quickly. That's a vaccine. I know which I prefer.