In 1950, Koprowski, Jervis, and Norton1 discovered that the oral administration of a rodentadapted laboratory strain of Type 2 poliovirus (the TN strain) to 20 non-immune children caused asymptomatic intestinal infection followed by the development of homotypic antibodies in blood. In 1960, reports presented at the Fourth Scientific Conference and International Symposium on Live Poliovirus Vaccines held in Moscow in May2 and at the Second International Conference on Live Poliovirus Vaccines held in Washington, D. C. in June3 disclosed that about 60 million people have been fed the attenuated live poliovirus vaccines in many parts of the world.
These mass vaccination programs have been preceded by a preparatory period of laboratory, clinical, and epidemiologic studies performed in a series of small, well-controlled trials in children and adults in the United States. Paradoxically enough, the "jump" from these limited studies to trials of national magnitude did not take place