Oral immunization against poliomyelitis

In the ten years since attenuated poliovirus was first administered to man for immunization against poliomyelitis, a vast body of experience has grown up and an attempt can now be made to assess the potentialities of oral poliovirus vaccine. The author of this paper seeks to answer two main questions: how safe are the strains now under study, and is oral vaccine effective in practice under the different conditions in which it may be used?From the information gained in large-scale trials involving a total of nearly 70 million people, he concludes that where poliomyelitis is predominantly a disease of infancy and early childhood the vaccines now available are safe both for the individual and for the community. The Sabin strains appear also to be safe for use in areas where the disease affects older children and adults; there is still not enough information to permit final conclusions to be drawn as to the safety of the Koprowski and Lederle strains in such areas.The evaluation of data on the efficacy of rural vaccines is beset with many problems, but the evidence of serological conversion rates suggests that, with one exception, there are no striking differences in efficacy between any of the strains when used in monovalent vaccines. However, 100% conversion cannot be expected in all circumstances from any oral vaccine given once only; repeated administration is clearly necessary, although it is still too early to say what the best vaccine schedule may be in any particular set of circumstances.While the problems yet to be solved are legion, great progress has nevertheless been made in the past decade, and the author looks forward to a steady extension of the use of live poliovirus vaccine and even to the eventual possibility of the eradication of poliomyelitis.