Until the year 1958, reports were available only on small numbers of persons vaccinated against poliomyelitis with live attenuated polio virus. Practically all information had been obtained from isolated or semi-isolated groups in institutions.
Early in 1958, we began one of the first field trials with live polio vaccine, a controlled study of vaccination in nonisolated infants and children of the city of Bern, Switzerland.1 Since then, more than 80,000,000 people in various countries have been vaccinated with live poliovirus, and many of the problems associated with this form of vaccine have been solved.
The purpose of our study was to obtain information about the following questions raised by this new method of vaccination:
The immunogenic properties of the live avirulent polio vaccine
The rate of intestinal infection and the duration of virus excretion
The spread of the vaccine virus from vaccinated persons to nonimmune contacts