It's not that simple, even if you are fighting it and would appear healthy, there is the thing called viral load that affects how you will still be infectious to others, especially early on when you may not show ANY symptoms, which is why social distancing is important until we have better testing protocol to determine whether you are effectively safe and won't infect immunocompromised or high risk groups
Some people cannot really do much, they are immunocompromised and there's nothing that can be done, especially with HIV/AIDS, which is a pandemic most people, myself included, don't realize is a pandemic, just not epidemic level anymore.
And we're not even certain the virus only has one strain in terms of immunity, one could beat one version of common flu and still catch another, that's virology 101