Combined vaccination of Haemophilus influenzae type b conjugate and diphtheria-tetanus-pertussis containing acellular pertussis

After the introduction of effective Haemophilus influenzae type b (Hib) con jugate vaccines, clinical practice has driven the development of combinatio n vaccines comprising Hib conjugates with the infant diphtheria-tetanus-per tussis (DTP) vaccines. However, when such combinations contain an acellular pertussis component (Pa), the antibody response to Hib is lower than that with separate injections and doubts have been raised about their efficacy. We believe that such concerns are unwarranted, since the serological correl ates of efficacy previously applied for Hib polysaccharide vaccines seem in appropriate for Hib conjugates. Furthermore, our own studies have shown tha t the lower antibody responses are not associated with impaired function of the antibodies induced, nor, and possibly more importantly, with the induc tion of immune memory against Hib. Therefore, with the proviso that careful clinical surveillance of Hib disease is maintained, we encourage the intro duction of DTPa-Hib combinations to facilitate the inclusion of Hib into th e already crowded childhood immunisation schedule.