It is not an analogy.
There was NO VACCINATION.in 1918... that is the obvious point.
the disappearance of Spanish Flu is rationalised to have been due to mutation..
however there is also a theory that those who died were presensitised to the"flu'
by a Russian flu in their childhood.
Perhaps the sudden disappearance is because most of the sensitised individuals died.
two of them were my great grandparents.. leaving three orphan kids
There is no point making a comparison.of Spanish flu.with Covid
For one there was NO VACCINATION
Furthermore we know diddly squat about the Flu except it killed adults. mostly in the 20-40 age range
Different pathogen.. different circumstances.. minimal information.
You might as well compare with the eradication of smallpox.
How fast was that?