I'm too tired and lazy at the moment to track down sources, but I know that scientifically speaking, having had Covid in the past means you have antibodies that know how to fight that specific version of Covid. It does nothing to protect you from the Delta Variant.

The vaccine is different. (Again, I know sources are needed. Sorry.) Because of how it works, because it uses mRNA instead of active or inactive samples of the virus, it offers broader protection.

It's not perfect, it doesn't work with 100% efficacy, and there are always going to be exceptions. But the vaccine gives you a fighting chance that prior infection does not.

Don't die, man.