[loudmax]

Different strains of Covid compete with each other because antibodies that block one version are very effective at blocking another. If you've recently had Omicron, your body is well prepared to fight off Delta.

If you've already had the flu, your body might have some level of preparedness against a Covid variant, but it's nowhere near the same level. Plenty of people who died from Covid had already experienced the flu at some point in their life. Covid variants compete with each other far more than they do with flu variants.