In 1954, John Franklin Enders and Peebles isolated measles virus from an 11-year-old boy, David Edmonston. Disappointed by polio vaccine’s development and involvement in some cases of polio and deathﾗwhat Enders attributed to Salk’s techniqueﾗEnders began development of measles vaccine. In Oct. 1960, an Enders team began trials on 1,500 mentally retarded children in New York City and on 4,000 children in Nigeria.