Kinetics of antibody response to Haemophilus influenzae type b vaccines

Serum antibodies to the capsular polysaccharide of Haemophilus influenzae t ype b (Hib) are effective in pl eventing or ameliorating invasive disease c aused by this human pathogen. Polysaccharide and conjugate (saccharide cova lently linked to protein carrier) vaccines have been developed which stimul ate the production of such antibodies. The polysaccharide-specific antibody concentrations in the sera of vaccine-naive adults and toddlers on days 1, 3, 7, 14 and 28 following immunisation with one dose of the Hib polysaccha ride vaccine (PRP, polyribosylribitol phosphate) or an oligosaccharide-CRM1 97 conjugate vaccine (HbOC, HibTITER(R)) were determined. Antibody response s occurred within 7 days of immunisation with the maximum response usually occurring 14 days post-immunisation, irrespective of vaccine or subject age . In this small study, a significant transient decline in pre-existing anti bodies was observed only in the groups receiving the polysaccharide vaccine and not in the groups receiving HbOC vaccine. Because of the small magnitu de of antigen-specific antibody decline and its transient nature, it is unl ikely that this observation has clinical significance.