>>13568330Of the ones that were properly tested over multiple years before widespread use? Not many. This isn't one of those vaccines though.
The typhoid vaccine was researched from 1896 to 1909, then not made available to the mainstream until 1914.
Yellow fever vaccine efforts started in 1918 and didn't produce a successful vaccine until 1937.
Polio vaccine development started in 1935, didn't produce a viable vaccine until 1953, and that wasn't accepted for use until 1955.
The chickenpox vaccine development began in the 1970s, then one was created in 1981, and it wasn't licensed in the US for mainstream use until 1995.
