Safety and immunogenicity of a prototype adjuvanted inactivated split-virus influenza A (HSN1) vaccine in infants and children

Objective: Highly pathogenic avian influenza A Virus (H5N1) is a leading candidate for the next influenza pandemic, and infants and children may play an important role in transmission in a pandemic. Our objective was to evaluate the safety and immunogenicity of a prototype inactivated aluminium adjuvanted, split-virus, clade 1 H5N1 vaccine (A/Vietnam/1194/2004/NIBRG-14) in infants and children aged >= 6 months to < 9 years. Methods: Healthy infants and children (N= 150) received two doses of 30 mu g or 45 mu g H5 HA with AIPO(4) adjuvant 21 days apart. Serum samples were collected for virus microneutralisation (MN) and haemagglutination inhibition (HI) assays on Days 0, 21, and 42. Six-month antibody persistence following second vaccine dose was assessed by MN, and cross-reactive HI antibodies to a clade 2 variant strain (IND05/RG2) were evaluated at Day 42. Findings: Both formulations were well-tolerated. Two doses of 30 mu g or 45 mu g H5 HA formulations elicited strong immune responses by both MN (98-99% >= 1:20) and HI assays (95-100% >= 1:32). with 80-87% of children having MN antibody persistence (>= 1:20) up to 6 months post-vaccination. Additionally, robust cross-Glade HI antibody responses were elicited following two doses. Interpretation: Two doses of prototype 30 mu g or 45 mu g aluminium-adjuvanted, H5N1 vaccines were highly immunogenic and well-tolerated, with considerable antibody persistence 6 months after the primary vaccination course. Additional cross-Glade HI antibody responses and an acceptable safety and tolerability profile support the use of the either candidate vaccine formulations in infants and children in the event of a pandemic [ClinicalTrials.gov identifiers: NCT00370864]. (c) 2008 Elsevier Ltd. All rights reserved.