Quality of the Haemophilus influenzae type b antibody response induced by DTPa/Hib combination vaccines

It has been repeatedly observed that mixing Haemophilus influenzae type b (Hib) conjugate vaccines with acellular pertussis-containing vaccines (DTPa) resulted in a reduced magnitude of the anti-PRP (polyriboseribitolphosphate) antibody response, compared to that obtained when Hib vaccines are administered separately and not mixed. Nevertheless, quality and functionality of the immune responses have been shown to be the same. With the purpose of investigating the quality of the anti-Hib immune responses that are elicited under different vaccination regimens, we report here on four primary and boosterbased pediatric clinical trials in which Hib vaccine was either mixed with DTPa or DTPw(whole cell pertussis)-based vaccines or co-administered. Our results show that avidity maturation of the antibodies was lower when primary vaccination involved DTPa mixed with Hib, compared to when DTPa and Hib were coadministered. No such difference was observed between mixed and separately administered Hib when associated with DTPa-HBV-IPV or DTPw-based vaccines. All different combinations and regimens elicited the same opsonophagocytic and bactericidal activity as well as the same ability to protect in a passive infant rat protection assay. The functional activity of mixed DTPa-based and Hib vaccines was similar to that of mixed DTPwbased/Hib combinations. In conclusion, in vitro and in vivo data as well as post-marketing vaccine effectiveness data attest for the ability of DTPa-based/Hib combination vaccines to effectively prevent Hibinduced disease in children. AC CE PT ED on S etem er 0, 2017 by gest httpcvi.asm .rg/ D ow nladed fom