What is often overlooked in defense against infections, even reinfection with a mutating pathogen, is that those who survive a novel infection likely have a strong immune system, as we all do unless we damage it from bad decisions or bad luck. If the new infection has antigens like a prior one, that speeds up the defense, but even if the new invader evades those stored defenses, healthy immune systems construct new ones. Surviving prior infection isn't just about stored antibodies or T cells but having a competent immune system that can create them as needed. Immune health can be, and often is, degraded, but can also be learned. Chemical manipulations with vaccines or therapeutics are useful for the weak, but are all inherently poisons and bring new risks. Better to learn to protect yourself naturally. The medical industry doesn't want to help. That's not their job, it's yours. They will actively discourage you from maintaining your health. Their lavish lifestyles depend on your sickness.