The National Library of Medicine has a very nice collection of U.S. Public Health Service Posters on their website, in an exhibit called the Iconography of a Contagion. There's a bunch of cool posters from the 20th Century, definitely fun to click through.
Poster credits go to Leonard Karsakov who designed this photomechanical print for the United States Public Health Service in 1945.
Thanks to StanleyMoons for the tip.
