There is a Big difference between covid and the spanish flu. No one was immune from the 1918 flu. It took the lives of people from toddlers to old folks. My great grandfather lost 4 kids all under the age of 4, his first wife age 25 and his second wife age 30. Then the flu took him at about age 45.
Also, the medicine available then was medieval compared to what we have today.
That’s why comparisons to the Spanish flu fall on deaf ears with me.