_*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.