Immunogenicity of a Triple Diphtheria-Tetanus-Whole Cell Pertussis Vaccine in Iranian Preschool Children

Background: Immunization against diphtheria, tetanus and pertussis has been applied in Iran since 1950. WHO suggests periodical evaluation of effectiveness of the triple diphtheria-tetanus-whole cell pertussis (DTwP) vaccine, worldwide. Objectives: To determine the immunogenicity of locally manufactured DTwP vaccine administered to preschool children in a number of health centers of Tehran in 2006. Methods: In this prospective study, 350 children aged 4-6 years were injected with DTwP vaccine manu-factured by Razi Institute of Iran. Blood samples were collected before and 2-4 weeks after the vaccination. The immunogenicity of the vaccine was assayed by measurement of specific antibodies using enzyme-linked immunosorbent assay (ELISA) technique. Results: Of the 337 children who were vaccinated, 99.4% and 100% had protective anti-diphtheria and anti-tetanus antibody titers, respectively. The vaccine response and seroconversion for pertussis was achieved in 70.3% of the subjects. The geometric mean titers (GMT) of the antibodies produced against diphtheria, tetanus and pertussis by DTwP vaccine were 7.76, 9.37 IU/ml and 30.20 EU/ml after booster vaccine dose, respectively. Conclusions: Comparison of the results obtained from this study with those of previous studies performed in other countries reveals that immunogenicity of diphtheria and tetanus components is similar to other vaccines, but the immunogenicity of pertussis vaccine was less efficient. The lower immunogenicity of DTwP against pertussis may be related to the bacterial strain used or the formulation protocol adopted for the vaccine preparation.