Immunogenicity and safety of purified chick-embryo cell rabies vaccine under Zagreb 2-1-1 or 5-dose Essen regimen in Chinese children 6 to 17 years old and adults over 50 years: a randomized open-label study

The aim of this Phase IIIb, open-label, randomized study was to demonstrate the non-inferiority of immune responses and to assess the safety of a purified chick-embryo cell rabies vaccine (PCECV) in healthy Chinese children (6 to 17 years) and older adults (≥51 years) following 2 alternative intramuscular (IM) simulated post-exposure prophylaxis (PEP) regimens: 4-dose Zagreb or 5-dose Essen regimen. Serum samples were collected prior to vaccination on Days 1 and 15 and on day 43 to assess immune response by rabies virus neutralizing antibody (RVNA) concentrations. Solicited adverse events (AEs) were recorded for up to 7 days following each vaccine dose, and unsolicited AEs throughout the entire study period. PCECV vaccination induced a strong immune response at Day 15, and the non-inferiority in immune response of the Zagreb vs. the Essen regimen was demonstrated in children and older adults. At Day 15,100% of children (N = 224), and 99% of subjects ≥51 years of age (N = 376) developed adequate RVNA concentrations (≥0.5 IU/mL); at Day 43 all subjects achieved RVNA concentrations ≥0.5 IU/mL, for both PEP regimens. The well-known tolerability and safety profile of the PCECV was again observed in this study following either Zagreb or Essen regimens. Rabies PEP vaccination with PCECV following a Zagreb regimen induced immune responses non-inferior to those of the Essen regimen, and had a similar safety and tolerability profile to the Essen regimen in Chinese children, adolescents, and adults over 51 years. ClinicalTrials.gov identifier: NCT01680016.