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Summary

Background

Invasive meningitis and pneumonia caused by Haemophilus influenzae type b (Hib) is an important cause of childhood mortality in countries where Hib vaccination is not routine. We evaluated the non-inferiority of a licensed Hib vaccine, PRP-CRM197 compared with a second licensed Hib vaccine, PRP-T, following the recommended Chinese immunisation schedule for infants between 6 months and 1 year of age.

Methods

In the first study phase, 6–12 month-old infants received two primary doses of either PRP-CRM197 (n = 335) or PRP-T (n = 335) vaccine administered 1 month apart. In the second study phase 8 months later, the same children received a single booster dose of vaccine identical to that use for priming (PRP-CRM197, n = 327; PRP-T, n = 333). Serum levels of anti-polyribosylribitol phosphate (PRP) antibodies were measured using enzyme-linked immunosorbent assay (ELISA). Non-inferiority of primary and booster doses was assessed in terms of percentages of subjects with anti-PRP antibody levels associated with providing short-term (≥ 0.15 μg/ml) and long-term (≥ 1.0 μg/ml) protection; the non-inferiority margin was set at −5%.

Results

PRP-CRM197 was demonstrated to be non-inferior to PRP-T. Anti-PRP antibodies levels ≥ 0.15 μg/ml and ≥ 1.0 μg/ml were achieved by 97% of infants in the PRP-CRM197 group and 98% of infants in the PRP-T group 1 month after primary immunisation, and by all subjects (100%) in both vaccine groups 1 month after booster administration. Safety profiles for both vaccines were similar; no serious adverse events, deaths or adverse events leading to withdrawal occurred during the study.

Conclusion

PRP-CRM197 was well-tolerated and immunologically non-inferior to a licensed comparator Hib vaccine in Chinese infants (Clinicaltrials.gov: NCT01044316 & NCT01226953).