Those that survive and recover from coccidiosis will build resistance to it (which ever strains they've been exposed to), but with the respiratory issues also, that can weaken the birds immune system leaving them susceptible. I just keep Corid on hand always now so that I have it when needed and can start treatment right away if I see symptoms. Young birds and birds weakened by something else are most susceptible, but it can happen to any. Your respiratory issues may be chronic, depends on what exactly is going on, and symptoms may recur. I wish you the best.