Who told you that part about the immune system? Rabies, HIV, Tetanus, and several other diseases beg to differ. Polio was a bit more recently stamped out since it was one of those diseases that tended to kill people. Small pox is another good example of diseases that don't leave you stronger. Covid19 is such a recent development there is no way to tell what the real long term effects will be for people of all age groups. So far the *first* people to die are those with complications and otherwise compromised immune systems. This just started and the infections have done nothing but go up. The large majority of people are taking this seriously and are trying to prevent spread, but a stubborn few have been determined to undermine the whole thing. The deaths were coming down, but have begun to rise. I understand that not everyone is paying as close of attention to this as I am, my immune system IS compromised. A quick internet search to the various CDC websites at the state and federal levels will show you that the case spike now is serious and real. The original death spike in the spring was really just NYC and Covid had not yet spread far and wide. Now there is spread nationwide at the county and even town level. The Easternmost part of the United States is having an outbreak. One of, if not the most, poor counties in the US is starting to have deaths as a result of folks giving up on social distancing back in the spring. Numerous churches across rural Maine have been spreading the virus.
The data is on a huge lag and there are countless statistics to fill the gaps in data, many of which are intentionally used to disinform people.
Many folks like to say there are people among us that are just "misinformed" which would be a benign, albeit unfortunate, circumstance. This is what happened in the spring. Now if people choose not to believe they have been "disinformed" which means a third party (ies) has been purposefully spreading falsehoods.