Evaluation of Red Cross Gamma Globulin as a Prophylactic Agent for Poliomyelitis

The plan and accomplishment of a series of three controlled field trials to evaluate the effectiveness of Red Cross gamma globulin in the prevention of poliomyelitis were described in the previous two papers (see this issue, pages 739 and 750). Effectiveness was to be determined by comparing the number of paralytic cases occurring in two groups receiving injections, one inoculated with gamma globulin, the other with gelatin. The groups were comparable, being essentially of equal size and presumably similar in all other respects, owing to the method of random distribution employed in packaging the two types of biologicals. Both biologicals were similarly labeled and looked alike. The serial number borne by each unit was the only means of identification. This serial number, obtained from the container of material inoculated, was entered on the record of each child. The key to the contents of all units was maintained in a central