> A third difference is that natural infection only exposes the body to the virus in the respiratory tract (unless the illness is very severe), while the vaccin

> A third difference is that natural infection only exposes the body to the virus in the respiratory tract (unless the illness is very severe), while the vaccine is delivered to muscle, where the immune system may have an even better chance of seeing it and responding vigorously. But the respiratrory tract is constantly exposed to the external world, wheras the muscles are typically protected by the skin... Therefore I find this fact counterintuitive.