Spanish Flu deaths were not really caused by a natural disease. The true cause of the Spanish Flu death rate was an experimental meningitus vaccine that was given to both soldiers and civilians.

https://rightsfreedoms.wordpress.com/2021/08/13/the-1918-spanish-flu-only-the-vaccinated-died/

The article says:

“Autopsies after the war proved that the 1918 flu was NOT a “FLU” at all. It was caused by random dosages of an experimental ‘bacterial meningitis vaccine’, which to this day, mimics flu-like symptoms. The massive, multiple assaults with additional vaccines on the unprepared immune systems of soldiers and civilians created a “killing field”.”

Those not vaccinated were not affected: https://www.newscientist.com/article/dn14458-bacteria-were-the-real-killers-in-1918-flu-pandemic/