Two hundred and eighty-seven sera from acute cases of poliomyelitis occurring in several epidemic areas over a period of four years were tested for neutralizing antibodies to the Lansing strain of virus. One hundred and one, or 35 per cent, were found to be positive.

The percentage of positive individuals in the different samplings varied from 89 to 0 and, in general, the groups having more positives were of a higher average age.

The average age of the positive individuals was greater than that of the negatives.

There was no correlation between the average day after onset for the bleeding with the percentage of positive individuals.

Tests with 234 sera from acute cases between the ages of 1 and 15 years showed a statistically significant lower per cent of individuals positive for Lansing virus neutralizing antibodies than a group of 221 healthy children in the same age range studied by Turner, Young and Maxwell.

Thirty-eight, or 73 per cent, of 52 associates had antibodies for the Lansing virus, closely approximating the percentage found in healthy non-associates.

In a study on 74 pairs of acute and convalescent sera, 39 or 52 per cent, were found to be positive in the acute stage. In 19 of these the titer remained the same for the later bleeding, in 3 the titer increased but in 17 there was a decrease in neutralizing antibody titers. Of the 35 individuals who were negative in the acute state, 30 remained negative and 5 developed antibodies during convalescence.

The significance of these phenomena is discussed.

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Aided by a grant from The National Foundation for Infantile Paralysis, Inc. Presented before the Epidemiology Section of the American Public Health Association at the 74th Annual Meeting in Cleveland, Ohio, November 14, 1946.

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