Albert Sabin a vaccine to prevent or mitigate the illness. The Sabin vaccine is an oral vaccine containing weakened forms of strains of polio viruses. In 1955, Salk's "killed" vaccine was released for use. It was effective in preventing most of the complications of polio, but did not prevent the initial intestinal infection. The Sabin vaccine is easier to give than the earlier vaccine developed by Salk in 1954, and its effects last longer. Sabin first tested his live attenuated oral vaccine at the Chillicothe Ohio Reformatory in late 1954. From 1956–1960, he worked with Russian colleagues to perfect the oral vaccine
Smallpox vaccine sheep were used. In the late 1940s and early 1950s, Leslie Collier, an English microbiologist working at the Lister Institute of Preventive Medicine, developed a method for producing a heat-stable freeze-dried vaccine in powdered form. Collier added 0.5% phenol to the vaccine to reduce the number of bacterial contaminants but the key stage was to add 5% peptone to the liquid vaccine before it was dispensed into ampoules. This protected the virus during the freeze drying process. After drying the ampoules were sealed under nitrogen. Like other vaccines, once reconstituted it became ineffective after 1–2 days at ambient temperatures. However,