Immune interaction between components of acellular pertussis-diphtheria-tetanus (DTaP) vaccine and Haemophilus influenzae b (Hib) conjugate vaccine in a rat model

We have previously shown that, consistent with clinical trial results, the immune response to a Haemophilus influenzae b (Hib) conjugate vaccine in a rat model was compromised and modulated when given combined with a DTaP 3 vaccine, as compared to both vaccines given separately. The present study extended our investigation to evaluate the immunogenicity of all DTaP 3 components in combined versus separate administration of Hib with DTaP 3 and investigated immune interactions between Hib and individual components of DTaP 3. Rats were immunised with Hib and DTaP 3 or with Hib and individual DTaP 3 components. Cellular and humoral immune responses to Hib and DTaP 3 components were evaluated. Our results indicate that the immunogenicity of DTaP 3 components was similar or greater in combined versus separate administration of Hib and DTaP 3. Moreover, combined administration of Hib and TT reduced immunogenicity of both Hib and TT. Hib immunogenicity was also significantly reduced when given combined with FHA and following adsorption to Al(OH) 3.