If you know how to kill a dog, you know how to kill a cow, even if some of the particulars are slightly different. Same with your immune system: If you know how to kill the H1N5 flu, you know how to kill the H3N5 flu, with a little bit of adjustment time period to alter the approach.

People like some native Australian tribes who've never had a coronavirus in their life can get fucked up by the WuFlu much more readily than someone who has fought off coronavirii their entire life. Even the lefty talking points agree on that one: Immune systems work.