[pumpkinhead]

This isn't a far-fetched as you might think. This damned virus seems to mutate at an alarmingly fast rate.

[hackerlight]

Which happened with the Spanish Flu. There was a mutation that made it more deadly for young people.

Such concerns also apply in the abstract to some unknown future virus which may work via a different mechanism to Covid and be capable of something far worse in terms of mortality*infectiousness.