Reduced immunogenicity of diphtheria and tetanus toxoids when combined with pertussis toxoid

Area of Science:

• Immunology
• Vaccinology
• Pediatric Infectious Diseases

Background:

• Diphtheria and tetanus toxoids (DT) are crucial components of routine infant immunization.
• The immunogenicity of combined vaccines can be influenced by the presence of additional antigens.
• Understanding these interactions is vital for developing effective vaccine formulations.

Purpose of the Study:

• To investigate the impact of pertussis toxoid on the immunogenicity of diphtheria and tetanus toxoids.
• To evaluate antibody responses to DT vaccines administered with or without pertussis toxoid in infants.

Main Methods:

• A double-blind efficacy trial of an acellular pertussis vaccine was conducted.
• Infants received either DT or DT combined with pertussis toxoid at 3, 5, and 12 months.
• Antibody concentrations for diphtheria and tetanus toxoids were measured at 1 month and 2 years post-vaccination.

Main Results:

• Geometric mean concentrations of diphtheria and tetanus toxoids were significantly lower in infants who received the DT-pertussis toxoid combination compared to those who received DT alone.
• This reduction in immunogenicity was observed both 1 month and 2 years after the third vaccine dose.
• Specifically, antibody levels for diphtheria toxoid were 3.58 IU/mL vs 4.76 IU/mL at 1 month and 0.10 IU/mL vs 0.15 IU/mL at 2 years.
• Tetanus toxoid levels were 2.66 IU/mL vs 4.42 IU/mL at 1 month and 0.18 IU/mL vs 0.38 IU/mL at 2 years.

Conclusions:

• Pertussis toxoid exerts a small but statistically significant suppressive effect on the immunogenicity of co-administered diphtheria and tetanus toxoids.
• These findings highlight potential antigenic competition within combined vaccines.
• Further research may be warranted to optimize the formulation of combined vaccines to maximize immune responses against all target diseases.