Mr. Tea
Let's Talk About Ceps
Added complication is that there was no longer one single SARS-COV-2 virus almost from the second the first person got ill, because it mutates so rapidly. I would think it's possible that even someone who's developed immunity to one strain could be floored by a new wave weeks or months later.
This diagram only takes us up to the end of February:

This diagram only takes us up to the end of February:
