Objective To evaluate the immunogenicity of a Haemophilus influenzae type b capsular-tetanus toxoid(Hib-TT) conjugate vaccine produced by Lanzhou Institute of Biological products(LIBP).Methods In an open-controlled,randomized trial,the eligible and consented 6-59 months-old young children injected 2 or 1 times 1 month apart with Hib-TT conjugate vaccine,the 3-5 months-old infants received 3 injections 1 month apart for primary immunization with Hib-TT or a licensed international Hib-TT conjugate vaccine as the control vaccine,and the boosting dose of two 3-5 months-old groups was injected at the 15-17months-old.The serum anti-Hib PRP IgG GMC in both groups after primary and boosting vaccination was measured by ELISA,the percentage of geometric mean concentration (GMC) ≥ 0.15 μg/ml and ≥ 1.0μg/ml was calculated,respectively.Results The Hib-TT conjugate vaccine produced in LIBP elicited satisfactory IgG antibody response in 3-59 months-old young children,the serum IgG GMC of anti-Hib PRP were 14.52 μg/ml(95％ CI:12.31-17.14)in 3-5 months-old,14.04 μg/ml(95％ CI:12.40-15.90) in 6-11 months-old.the ratios of IgG antibody concentration ≥ 1.0 μg/ml were 96.90％ (95％ CI:92.50-99.20) in study vaccine group and 98.55％ (95％ CI:92.20-99.90) in the control vaccine after 3 doses,respectively.100％ of the 6-11 months-old young children who injected 2 times with the Hib-TT conjugate vaccine had IgG antibody concentration ≥ 1.0 μg/ml (95％ CI:95.94-100.00),91.35％ (95％ CI:86.13-99.48) of recipients in 12-59 months-old young children induced the IgG antibody concentration ≥ 1.0 μg/ml after a single dose.The serum IgG antibody GMC in recipients who received the study or and control vaccines increased from 6.27 μg/ml (95 ％ CI:5.28-7.48) and 5.57 μg/ml (95 ％ CI:4.45-6.97)at pre-boosting injections to 63.14 μg/ml(95％ CI:52.14-76.47) and 73.48 μg/ml (95％ CI:57.37-94.11) one month after boosting injection,respectively.The percentage of IgG antibody concentration ≥ 1.0 μg/ml increased from 76.35％ and 79.55％ of pre-boosting to 100％ in the two groups after booting dose.Although the serum IgG GMC in two groups appeared to decline markedly,it remained at a relatively high levels of 25.02 μg/ml (95％ CI:20.51-30.48) in the study vaccine and 23.64 μg/ml (95％ CI:18.40-30.43) in the control vaccine,and all of the recipients in both groups remained 100.0％ of IgG antibody concentration ≥ 1.0 μg/ml.Conclusion The study vaccine elicited a protective immune response and induced the IgG antibody concentration which indicated long-term protection of anti-Hib PRP in 3 to 59months-old infants and young children.

Objectives To evaluate the safety and immunogenicity of Haemophilus influenzae type b capsular-tetanus toxoid(Hib-TT) conjugate vaccine.Methods In an open-controlled,randomized trial,the eligible and consented infants of 3 to 5 months-old received 3 doses of Hib-TT or a licensed Hib-TT conjugate vaccine(Anerbao) as the control vaccine to evaluate safety; The serum anti-Hib PRP IgG antibody mean geometric concentration (GMC) in both groups after primary and boosting vaccination were measured by ELISA.Results No apparent difference in the frequency of total adverse reactions observed between two groups (study vaccine 23.85％ vs.comparator 31.40％) (x2=0.5,P＞0.05).The mild and severe fever reaction of both vaccines was 3.67％ and 4.48％ respectively,with no significant difference.The local reactions including erythema,swelling and induration reported was 1.22％ in study vaccine group.After 3 injections,the serum anti-Hib PRP IgG antibody GMC was 6.6686 μg/ml in study group and 7.5346 μg/ml in control group,with no significant difference in both of the antibody GMC (x2 =0.147,P=0.702).After one dose boosting injection,the serum antibody GMC in study group increased from 2.6396 μg/ml of preboosting to 6.2044 μg/ml of post-boosting.Conclusion The Hib-TT conjugate vaccine is proved to be safe in 3-5 months-old infants.The primary immune schedule for 3-5 months-old infants of 3 injections 1 month apart with the Hib-TT conjugate vaccine could induce IgG antibody response against Hib PRP with the GMC of long-term protection concentration in serum.A boosting dose after primary vaccination elicited obviously immunological memory.