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Comparison of five different vaccination schedules with Haemophilus influenzae type b-tetanus toxoid conjugate
S Kurikka1, H Käyhty, L Saarinen
1National Public Health Institute, Helsinki, Finland.
Insights
Two doses of Haemophilus influenzae type b (Hib) conjugate vaccine (PRP-T) provide adequate infant protection up to 18 months. A three-dose schedule offers superior antibody concentrations compared to two-dose schedules.
Area of Science:
- Immunology
- Vaccinology
- Pediatrics
Background:
- Haemophilus influenzae type b (Hib) conjugate vaccines are crucial for preventing invasive Hib disease in infants.
- Optimal vaccination schedules are essential for achieving robust and sustained immune responses.
Purpose of the Study:
- To compare the immunogenicity of five different vaccination schedules for the Haemophilus influenzae type b (Hib)-tetanus toxoid conjugate (PRP-T) vaccine in infants.
- To evaluate the duration of antibody persistence following different PRP-T vaccination schedules.
Main Methods:
- A study involving 196 infants compared four two-dose schedules (1-3, 2-4, 2-6, 4-6 months) and one three-dose schedule (2, 4, 6 months) for the PRP-T vaccine.
- Vaccines were administered concomitantly with diphtheria-tetanus-pertussis (DTP) and inactivated polio vaccine (IPV).
- Anti-Hib antibody levels were measured by radioimmunoassay at various time points, including pre-immunization, post-vaccination, and up to 12-24 months of age.
Main Results:
- All tested PRP-T vaccination schedules demonstrated immunogenicity in infants.
- Two doses of PRP-T vaccine were sufficient to maintain protective antibody levels (≥0.15 µg/ml) in most children up to 12-18 months.
- A three-dose schedule elicited significantly higher final antibody concentrations compared to the optimal two-dose schedule.
Conclusions:
- The PRP-T vaccine is immunogenic when administered with DTP and IPV in schedules starting from 1 to 4 months of age.
- Two doses of PRP-T vaccine provide adequate protection against Hib disease for at least 12-18 months post-vaccination.
- While two doses are effective, a three-dose schedule results in higher sustained antibody levels.
Objective:
To compare seroresponses to five different vaccination schedules for Haemophilus influenzae type b (Hib)-tetanus toxoid conjugate (PRP-T) vaccine in infants.
Design:
Four different two-dose schedules were compared, with doses given at 1 and 3 months, 2 and 4 months, 2 and 6 months, or 4 and 6 months of age. One group received three doses at 2, 4, and 6 months of age. The PRP-T vaccine was given in the same syringe with diphtheria-tetanus-pertussis (DTP) vaccine; inactivated polio vaccine (IPV) was given in a separate syringe. Anti-Hib polysaccharide antibodies were measured by radioimmunoassay in sera taken before each immunization, 1 month after the second dose, at 7 and at 12 to 24 months of age.
Subjects:
A total of 196 healthy infants were enrolled between November 1990 and November 1992.
Results:
After one dose of PRP-T there were no significant differences in geometric mean antibody concentrations (0.09 to 0.13 microgram/ml) or in fold responses among the schedules. The response to the second dose was significantly higher than the response to the first dose given at the same age. The geometric mean antibody concentration was lower in the group vaccinated at 1 and 3 months than in the groups vaccinated at 2 and 4 months, 2 and 6 months, or 4 and 6 months. The three-dose schedule resulted in a significantly higher final antibody concentration than the best two-dose schedule (p <0.001). In most children (64% to 93%), the antibody concentration remained at least 0.15 microgram/ml up to the age of 12 to 24 months.
Conclusions:
The Hib conjugate vaccine, PRP-T, administered concomitantly with DTP vaccine and IPV, was immunogenic with schedules starting at 1 to 4 months of age. Two injections of PRP-T vaccine were immunogenic enough to maintain protection up to 12 to 18 months of age.