ANTIBODY-RESPONSES OF 3 HAEMOPHILUS-INFLUENZAE TYPE-B CONJUGATE VACCINES AFTER ONE, 2 AND 3 DOSES IN FILIPINO CHILDREN

Differences in the magnitude of antibody response after one, two or th ree doses of Haemophilus influenzae type b conjugate vaccines have bee n reported which may influence decision-making regarding which vaccine should be used This is of particular importance in developing countri es where children may not receive a full immunization series and the v accination schedule may be delayed Serum antibody responses to three H ib capsular polysaccharide protein conjugate vaccines (PRP-OMP, HbOC a nd PRP-T) were evaluated in 102 Filipino infants. Vaccination was carr ied out at 6, 10 and 14 weeks of age based on the national Expanded Pr ogramme on Immunization (EPI) schedule together with diphtheria-tetanu s-pertussis, hepatitis B and oral poliomyelitis vaccines. Sera were co llected at 6 weeks and I month after each vaccination. Anti-Hib polysa ccharide antibody concentrations were determined by Farr-type radioimm unoassay (RIA) and enzymeimmunoassay (EIA). Following the first dose, the geometric mean concentrations (GMC, mu g ml(-1)) for PRP-OMP, HbOC and PRP-T were 0.69, 0.27 and 0.38, respectively. After two doses, th ere was a significant response (P<0.05) to PRP-OMP and PRP-T (0.89 and 1.47) but not for HbOC (0.37), Differences in the GMC after the prima ry series were significant (pairwise P < 0.05). GMC was highest for PR P-T (4.0), followed by HbOC (1.6) and PRP-OMP (1.1). All three Hib vac cines were immunogenic when given in the local EPI schedule in Filipin o infants although significant differences in the kinetics and! magnit ude of antibody responses were noted. The anti-Hib antibody concentrat ions determined by RIA and ELA were also compared in order to validate the latter for use in laboratories where if is feasible. There was a good correlation (r(2) = 76%; P = 0.0001) in the Hib antibody titres o btained by both assays. (C) 1998 Elsevier Science Ltd. All rights rese rved.