Immunogenicity and reactogenicity of two diphtheria-tetanus-whole cell pertussis vaccines in Iranian pre-school children, a randomized controlled trial.

The present study was undertaken to compare the immunogenicity and reactogenicity of two diphtheria-tetanus-whole cell pertussis (DTwP) vaccines administered to Iranian preschool children. In this randomized, double-blind and multicenter prospective study, 672 children aged 4–6 y were administered with either a local DTwP vaccine (DTwP-Local) (n = 337) or a commercial vaccine (DTwP-Pasteur) (n = 335). All subjects received DTwP vaccine at 4–6 y of age, following the national immunization schedule of Iran. Blood samples were collected before and 2–4 weeks after the vaccination. Immunogenicity of each vaccine was assessed by ELISA using commercial kits. Reactogenicity was assessed by the parents for seven days post-booster using diary cards. The geometric mean titers (GMTs) of the antibodies induced against diphtheria and tetanus by DTwP-Local were 7.7 and 9.4 IU/ml and those of DTwP-Pasteur were 8.2 and 8.6 IU/ml, respectively. There was no significant difference between the immunogenicity of the two vaccines against diphtheria and tetanus. The GMTs of antibodies produced against pertussis were 30.2 EU/ml for DTwP-Local and 47.9 EU/ml for DTwP-Pasteur vaccines (p 37.5°C) were the most frequent local and systemic reactions observed after the vaccination. All local and systemic reactions observed after vaccination were significantly higher in subjects immunized with DTwP-Local vaccine. Immunogenicity against diphtheria and tetanus was similar for the two vaccines, but immunogenicity of the local vaccine against pertussis was significantly less efficient than that of DTwP-Pasteur. This difference and the higher side effects of the DTwP-Local vaccine could be due to the bacterial strain or the preparation or formulation protocol of the local pertussis vaccine.