IMMUNOGENICITY OF HAEMOPHILUS-INFLUENZAE DIPHTHERIA CRM-197 PROTEIN CONJUGATE VACCINE (HBOC) IN LIBYAN INFANTS

The immunogenicity of the HbOC, a Haemophilus influenzae type b conjug ate vaccine, was evaluated in a randomized clinical trial of Arab chil dren resident in Tripoli. The HbOC vaccine was given as part of a thre e-dose series at 2, 3 and 4 months of age together with hepatitis B, O PV and DPT to 90 children. Anti-H. influenzae antibody levels were com pared with 81 infants receiving hepatitis B, OPV and DPT but not the H bOC vaccine. The immunogenicity and safety of HbOC was as high as that observed in industrialised countries. There were no major complicatio ns, and fever and temporary local discomfort were observed in fewer th an approximately 2% of the infants. Infants receiving the HbOC vaccine had an increase in Hib antibodies with only one dose. Geometric mean anti-Hib antibody levels were 0.41, 1.36 and 2.91 mg/ml after one, two and three doses. After two doses, all children had antibody levels ab ove 0.20 mg/ml and the lowest antibody concentration was 0.80 mg/ml. A ntibody levels in our children are similar to those observed in Europe and the USA and it is thus likely that HbOC will provide good clinica l protection in this population. As most of the children develop antib ody titres above or near I mg/ml, it is likely that they are protected even with two doses of the vaccine. The anti-Hib antibody levels obse rved are similar to those in studies from Europe where hepatitis B vac cine is not routinely given.