studies on a hibtetanus toxoid conjugate vaccine effects of coadministered tetanus toxoid vaccine of administration route and of combined administration with an inactivated polio vaccine a freezedried tetanus toxoid t conjugated haemophilus influenzae type b hib vaccine was reconstituted in either diphtheria toxoid d dt or a combined dt and inactivated polio vaccine ipv and administered in an open randomized trial either intramuscularly im or subcutaneously sc to 287 swedish infants at three five and 12 months of age when not included in the mixture ipv was administered sc at a separate site the geometric mean concentrations of hib antibodies after primary and booster vaccinations were 10 and 116 microgml respectively with no differences related to coadministration of the carrier protein t antibodies against t were induced by the t conjugated hib vaccine hibt alone in 6995 infants aged six months and in 8793 children aged 13 months although infants receiving both hibt and t had significantly higher concentrations antibody responses to hib d t or polio were not negatively influenced by administration route or by mixing with ipv except that the mixed vaccine dtipv induced lower antipolio gm titers after primary vaccination than did separate ipv more local reactions were induced by the sc than by the im route pvalues from 0001 to 001 slight increases in rates of local reactions and febrile events 38 degrees c occurred by order of dose the low hib antibody concentrations after the first two doses in this and other swedish studies are unlikely to be of clinical relevance the tetanus antibody response from t as a carrier protein alone was not sufficient for basic tetanus immunization but should be considered in future use of additional t conjugated vaccines