DOES TETANUS IMMUNE GLOBULIN INTERFERE WITH THE IMMUNE-RESPONSE TO SIMULTANEOUS ADMINISTRATION OF TETANUS-DIPHTHERIA VACCINE - A COMPARATIVE CLINICAL-TRIAL IN ADULTS

In the management of wounds, sometimes it is recommended to give an adult-type tetanus-diphtheria (Td) vaccine dose plus tetanus immune globulin (TIG). Sixty and 59 healthy young adults previously immunized against tetanus (T) and diphtheria (D) were randomized to receive intramuscularly either Td vaccine alone (group 1) or Td vaccine plus 500 IU of TIG (group 2) simultaneously Antitoxin response was assessed after 4 weeks and 4 months. Circulating antibodies were measured by enzyme-linked immunosorbent assay (ELISA). The cutoff of these tests was 0.1 IU/mL. Titers of 0.1 IU/mL or greater were considered protective. For geometric mean titers (GMT), antibody titers below the cutoff of the assay were given, arbitrarily, 0.05 IU/mL. At 4 weeks, 98% or more of the subjects in group 1 had circulating T and D antitoxin levels of 0.1 IU/mL or higher; in group 2, 95% and 90% of the subjects had titers above this limit for T and D, respectively. At 4 months, these percentages were 98% and 95% for T antitoxin levels in groups 1 and 2, respectively; whereas 96% and 88% of the subjects in groups 1 and 2 had D antitoxin levels of 0.1 IU/mL or higher, respectively. Significantly (P < .05) higher GMTs were seen at the 4-week assessment (hut not at 4 months) in group 1, as compared with group 2, in both T and D antitoxin levels (9.91 IU/mL versus 5.60 IU/mL for T antitoxin, and 2.86 IU/mL versus 1.45 IU/mL for D antitoxin). This finding resulted from those participants with low (<0.1 IU/mL) prevaccination antibody titers. Among these, D antibody GMTs at 4 weeks were 1.94 IU/mL and 1.06 IU/mL for those receiving Td vaccine or Td vaccine plus TIG, respectively; corresponding values for T antibody GMTs at 4 months were 3.53 IU/mL and 0.64 IU/mL (P = .02), respectively. Concurrent administration of TIG with Td vaccine interferes with the immune response to T toroid in subjects with low prevaccination antibody titers. Further studies are needed to confirm these results.