Potency of fragmented IgG: two studies of postexposure prophylaxis in type A hepatitis.

To determine the effect of fragmentation on potency of immune globulin preparations, two comparisons were carried out. In one study, the immune globulin was derived from American plasma; in the other, the source was Israeli plasma. In each of the two studies, three materials were given to household contacts of icteric hepatitis: (1) human albumin as a placebo; (2) immune globulin with the IgG intact; and (3) immune globulin of the same lot with the IgG deliberately fragmented by added fibrinolysin. Comparable reductions in secondary attack rates were achieved with fragmented and unfragmented materials from both lots. Fragmentation, therefore, had no deleterious effect. In addition, it was found that American globulin is comparable to Israeli globulin for protection against strains of Type A hepatitis prevalent in Israel. Administration in the second half (last 15 days) of the incubation period did not reduce the frequency of icteric disease.