This seems contradictory to empirical data, tge empirical data shows low symptoms and less severity all round, and we already have identified the high risk individuals, this has not changed since the beginning, which has now been moved to early July 2019 that serum from cancer patients had antibodies in their samples taken. Which means it was already spreading fast and means that tearibg for previous infections would have been the most important process to follow, and as these individuals became known less and less individuals are at risk.
This is what needs to happen when the next pandemic cones, we have been told it will so get ready.