Status of Field Trials With an Orally Administered, Live Attenuated Poliovirus Vaccine

Between October, 1958, and early September, 1959, about 11 million children outside the United States received by mouth a vaccine prepared from strains of poliovirus that had been selected and studied in this country by the author. Preliminary studies had shown that the establishment of these strains in susceptible persons was neither associated with any distinct illness nor was it followed by detectable late manifestations in the nervous system. The spread of the three vaccine strains was comparable to that of the naturally occurring viruses. The presence of other viral intestinal infections sometimes suppressed the multiplication of the orally administered poliovirus vaccines. In the absence of interference, antibody was demonstrable within 7 to 10 days after infection. A large body of evidence now indicates that the live vaccine is safe for both the vaccinated children and the community.