Spanish Flu did not kill 50,000,000...

Spanish Flu did not kill 50,000,000. Vaccines did. In the deadly Spanish influenza pandemic of 1918-19, investigators attempted to develop vaccines to prevent influenza, though they had not yet correctly identified the causative pathogen. A variety of killed whole cell bacterial vaccines were tested; these vaccines included Bacillus influenzae (now know as Haemophilus influenzae) and strains of pneumococcus, streptococcus, staphylococcus, and Moraxella catarrhalis bacteria. These vaccines would certainly not have prevented influenza infection--as we know now, the pandemic was caused by a new strain of the influenza A virus. Influenza viruses would not be isolated and identified until the 1930s, and the first commercial influenza vaccines were not licensed in the United States until the 1940s.

And in case you're wondering, yes the vaccine was developed in Fort Detrick. Where just about every bio weapon has originated from.