With the menace of polio growing, Sabin and other researchers, most notably
Jonas Salk in
Pittsburgh and
Hilary Koprowski and
H. R. Cox in
New York City and
Philadelphia, respectively, sought a vaccine to prevent or mitigate the illness. This was complicated because there were multiple strains of the disease. In 1951, the
National Foundation for Infantile Paralysis's typing program confirmed the existence of three main
serotypes of poliovirus, since known as type 1, type 2, and type 3. By carrying out autopsies of polio victims, Sabin was able to demonstrate that the poliovirus multiplied and attacked the intestines before it moved to the central nervous system. This also suggested that polio virus could be grown in other tissues besides embryonic brain tissue, leading to easier and cheaper methods of vaccine development. This provided the critical impetus for allowing large-scale clinical trials of OPV in the United States in April 1960 on 180,000 Cincinnati school children. The mass immunization techniques that Sabin pioneered with his associates effectively eradicated polio in Cincinnati. Against considerable opposition from the
March of Dimes Foundation, which supported use of Salk's relatively effective killed vaccine, Sabin prevailed on the
Public Health Service (PHS) to license his three strains of vaccine. While the PHS stalled, the USSR sent millions of doses of the oral vaccine to places with polio epidemics, such as Japan. because the oral polio vaccine had a bitter, salty taste (inspiring
Robert B. Sherman's lyrics to
A Spoonful of Sugar (Helps the Medicine Go Down) for the
1964 film Mary Poppins). In 1964, a single trivalent OPV containing all three viral serotypes was approved. The Sabin vaccine became the predominant method of vaccination against polio in the United States for the next three decades. It broke the chain of transmission of the virus and allowed for the possibility that polio might one day be eradicated. == Philanthropy ==