Safety and immunogenicity of two Haemophilus influenzae type b conjugate vaccines
Objectives. Haemophilus influenzae type b (Hib) infection remains a major public health problem inthe developing world. We evaluated the safety and immunogenicity of a new PRP-CRM197 conjugate Hib vaccine (Vaxem Hib, Chiron Vacdnes), compared with theHibTITER vaccine (WyethLederle Vaccines), following the World Health Organisation (WHO)'s accelerated schedule which allows 4-week intervals between doses.
Study design. A phase II, observer-blind, multicentre, randomised, controlled, non-inferiority study.
Methods. In total, 331 babies were immunised with either Vaxem Hib (N = 167) or HibTITER (N = 164) vaccine at 6, 10 and 14 weeks of age, in parallel with oral polio, diphtheriatetanus- pertussis and hepatitis B vaccines. Postimmunisation reactions were recorded after each immunisation and arfollow-up visits. Anti-polyribosylribitol phosphate (PRP) antibodies were measured using enzyme-linked immunosorbent assays (ELISAs) before and 1 month after the third immunisation.
Results. Overall, there was no significant difference in the anti-PRP levels between the two groups .. One month after the third immunisation, 76% of vacdnees in the Vaxem Hib group and 70% in the HibTITER group hadanti-PRP antibody mres i:: 1.0 vg/ tnl, while 96% of the Vaxem l-Iib group and.90% of the HibTITER gn;mp d.e!l}onstrated a),lt1- PRP antibody titres;:: 0.15 vg/ml. The geometric me<t:ntitre at day 90 was 3.77 pg/ml for the VaxemHib and 3.0 Jlg/Inl for the HibTITER groups. Although the Vaxem Hib vaccine produced more redness (6% versus 1 %; p = 0.006) and swelling (5% versus 1%, p = 0.037), overall it was well tolerated compared with the B:ibTITER vaccine. There wa~ no significant difference in vaccine-relateq elevated temperature (;:: 38°(:) between the two groups (p = 0. 11),
Conclusion. Both vaccines showed comparable safety llJ:\d immunogenicity profiles when administered to SouthAfrican babies at 6, 10 and 14weeks of age.