Production of formalinized poliomyelitis vaccine (Salk-type) on a semi-industrial scale.

This article describes a semi-industrial method for the production of formalinized poliomyelitis vaccine developed during 1956. The general technique followed that originally devised by Salk with modifications developed locally. The vaccine was tested for safety and innocuity according to the Minimum Requirements laid down by the United States Public Health Service. Seitz filtration was found to be essential for the production of a non-infectious vaccine; filtration through glass filters proved to give inconsistent results. High initial virus titres, proper filtration methods, and the use of a sensitive tissue-culture system for safety testing were considered to be of prime importance for the production of a safe and effective vaccine. Over 60 000 infants and young children were inoculated with this vaccine in a country-wide immunization programme during the winter and spring of 1957. No untoward effects were noted; an immunological evaluation of its performance in those inoculated is in progress.