This vaccine was formulated specifically to combat the H2N2 “Asian strain” which caused the Asian Flu pandemic of 1957-58, our first pandemic since 1918, resulting in 70,000 deaths in US. Scientists at Walter Reed Medical Center obtained a sample of the virus in April 1957, and the first vaccines were ready for distribution by September. Thimersol, a mercury derivative, is listed as a preservative. It would eventually be eliminated from most vaccines due to fear that it may cause neurological damage to infants.