SAFETY AND IMMUNOGENICITY OF HAEMOPHILUS-INFLUENZAE VACCINE (TETANUS TOROID CONJUGATE) ADMINISTERED CONCURRENTLY OR COMBINED WITH DIPHTHERIA AND TETANUS TOXOIDS, PERTUSSIS-VACCINE AND INACTIVATED POLIOMYELITIS VACCINE TO HEALTHY INFANTS AT 2, 4 AND 6 MONTHS OF AGE

The safety and immunogenicity of Haemophilus influenzae vaccine (tetanus toroid conjugate (PRP-T)) administered concurrently in separate sites or mixed in the same syringe with diphtheria and tetanus toxoids, pertussis vaccine and inactivated poliomyelitis vaccine were assessed in 439 infants at 2, 4 and 6 months of age. The proportions with local redness, tenderness and swelling in the separate and combined groups were 18% vs. 11% (P < 0.001), 27% vs. 24% and 15% vs. 13%, respectively. Systemic reactions occurred at similar rates in both groups. The combined vaccine induced tetanus and diphtheria antitoxin titers greater than or equal to 0.01 IU/ml in 99.5 and 99.1% of infants, pertussis agglutinin titers greater than or equal to 64 in 92.4%, anti-polyribosylribitol phosphate titers greater than or equal to 0.15 mu g/ml in 93.8% and greater than or equal to 1.0 mu g/ml in 75% and polio-neutralizing titers greater than or equal to 8 in > 98% of infants. However, antibody concentrations to PRP-T, some pertussis antigens and tetanus toroid were significantly lower after combined than after separate injections of DPT/diphtheria and tetanus toxoids, pertussis vaccine and inactivated poliomyelitis vaccine and PRP-T. The clinical significance of these differences is not known, but the interactions observed among the components of the pentavalent vaccine may be of concern because they might influence antibody persistence until the fourth dose is administered.