What do you mean? Immunity of naturally infected individuals has been tracked far longer than five months, with both empirical evidence of lasting immunity along with obvious community evidence.
Do you know why the infection rate in San Francisco was so low? There was already a ton of natural immunity due to community spread. The majority of my office in downtown SF caught COVID in January 2020, which was confirmed by negative influenza A & B tests followed by positive antibody tests once they were made available.
What is particular disturbing to me is that, despite the fact that the CDC estimates total infections to be over a third of the U.S. population (and that estimate only accounts for February 2020 onward and doesn't include last two months), natural immunity is never, ever discussed by policy makers. Why? That's a massive amount of natural immunity that continues to be purposely ignored.