Studies of the Change of Antibody Titers after Vaccination of Haemophilus Influenzae PRP-T Conjugate Vaccine

ABSTRACT

PURPOSE: This study was carried out to survey the serum anti-PRP titers after the completion of a primary series with 3 doses of the PRP-T conjugate vaccine(ACT-HIBTM), to evaluate the necessity of booster vaccination. METHODS: One hundred twenty healthy infants who went for consultations at Moon Hwa hospital between December 1999 to May 2001 were vaccinated at two, four and six months after birth. The serum antibody levels were measured at 7-8 months and 19-20 months of age by the "Farr" type of radioimmunological method at Aventis Pasteur International in France. RESULTS: The geometric mean of Anti-PRP titers were 24.6 microgram/mL at 7-8 months and then fell to 2.10 microgram/mL at 19-20 months. Minimum Anti-PRP titer was 0.75 microgram/mL at 7-8 months, and 0.1 microgram/mL at 19-20 months. Maximum Anti- PRP titer was 99.2 microgram/mL at 7-8 months, and 9.1 microgram/mL at 19-20 months. Subjects of Anti-PRP titers more than 0.15 microgram/mL were 100% at 7-8 months, and 97.0% at 19-20 months, and subjects of Anti-PRP titers more than 1.0 microgram/mL were 98.3% at 7-8 months, and 61.6% at 19-20 months. CONCLUSION: The Anti-PRP titers at 7-8 months were very high but rapidly decreased at 19-20 months of age, so the necessity of booster vaccination could be considered in Korean children.