A description is given of a precipitin test, using potent non-infectious antigens, which can be performed in laboratories not specializing in virology. Trial of the method as a diagnostic procedure gave positive results in 100% of a series of 50 patients with acute poliomyelitis. Precipitation lines, almost always sharply defined and intense, were obtained in 89% of 33 sera within 3–8 days of onset of acute poliomyelitis and in all sera after the 8th day. In positive cases precipitation bands usually appeared within 24 hr. after starting the test. In all instances precipitation was homotypic with the type virus isolated from stools. Double bands appeared in very recent cases but only with homotypic precipitins. Single heterotypic lines appeared in 12 cases due to previous infection or perhaps due to infection by virus strains with common antigens. All control patients with nervous system disease other than poliomyelitis or with infection by Coxsackie or ECHO viruses and all control test animals gave negative results. Of 240 poorcommunity schoolchildren who had taken monovalent oral poliovaccine 4½ months previously, 80% had precipitins for Type 1, but less than 5% showed marked reactions. The sera from the remainder gave only weakly positive results. Contrasting with transience of precipitins, neutralizing antibodies persisted in nearly 100% of children tested.

The precipitin test was used to study antibody response to ingestion of trivalent oral vaccine (prepared and issued by the Poliomyelitis Research Foundation, Johannesburg). More than half (54 %) of 90 students who received the vaccine had positive precipitin-test results; most often these results appeared during the 2nd week after ingestion. In this positive group 54 % showed multiplication of at least two types and 12 % showed multiplication of all three types poliovirus.