Safety and immunogenicity of an inactivated thimerosal-free influenza vaccine in infants and children.

OBJECTIVE: Few prospective studies of inactivated split virion influenza vaccine have been conducted in infants and children. Our objective was to evaluate the safety, reactogenicity and immunogenicity of a thimerosal-free inactivated influenza vaccine (Fluvax; CSL Limited, Parkville, Australia) in children aged 6 months to <9 years. METHODS: A prospective, open-label, phase III clinical trial was conducted in 298 healthy children previously unvaccinated with influenza, commencing in the Southern Hemisphere 2005 autumn. Participants were divided into two groups (Group A: > or =6 months to <3 years; Group B: > or =3 years to <9 years), and received two doses of the 2005 vaccine, and one dose of the 2006 vaccine one year later (Group A: 0.25 ml per dose; Group B: 0.5 ml per dose). Vaccine safety and reactogenicity was evaluated for 30 days after each dose. Immunogenicity was assessed using hemagglutination inhibition and single radial hemolysis assays. RESULTS: There were no withdrawals due to adverse events (AEs). The majority of solicited local and systemic AEs were of mild severity. A maximum intensity of severe was reported for injection site pain and fever by only 3.0% and 3.4% of participants, respectively. The vaccine was immunogenic for all antigens, with > or =95% of both younger and older children achieving seroprotection after dose 2. CONCLUSIONS: This thimerosal-free inactivated influenza vaccine had a favorable safety profile and was immunogenic in children aged > or =6 months and <9 years. Primary and booster vaccination produced consistently immunogenic responses including in children under 3 years of age receiving 0.25 ml doses of vaccine.

Safety and immunogenicity of a prototype adjuvanted inactivated split-virus influenza A (H5N1) 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 > or =6 months to < 9 years. METHODS: Healthy infants and children (N=150) received two doses of 30 microg or 45 microg H5 HA with AlPO4 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 (INDO5/RG2) were evaluated at Day 42. FINDINGS: Both formulations were well-tolerated. Two doses of 30 microg or 45 microg H5 HA formulations elicited strong immune responses by both MN (98-99% > or =1:20) and HI assays (95-100% > or =1:32), with 80-87% of children having MN antibody persistence (> or =1:20) up to 6 months post-vaccination. Additionally, robust cross-clade HI antibody responses were elicited following two doses. INTERPRETATION: Two doses of prototype 30 microg or 45 microg aluminium-adjuvanted, H5N1 vaccines were highly immunogenic and well-tolerated, with considerable antibody persistence 6 months after the primary vaccination course. Additional cross-clade 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.

Phase I and II randomised trials of the safety and immunogenicity of a prototype adjuvanted inactivated split-virus influenza A (H5N1) vaccine in healthy adults.

OBJECTIVE: The primary objective was to evaluate the safety and immunogenicity of a prototype inactivated, split-virus H5N1 (avian influenza A) vaccine. A secondary objective was to assess the cross-reactivity of immune responses to two variant clade 2 H5N1 strains. METHODS: In two randomised, dose comparison, parallel assignment, multicentre trials conducted in Australia, healthy adult volunteers received two doses of 7.5 microg or 15 microg H5 haemagglutinin (HA) vaccine+/-AlPO4 adjuvant (phase I trial; N=400) or two doses of 30 microg or 45 microg H5 HA with AlPO4 adjuvant (phase II trial; N=400). Revaccination with a booster dose was offered 6 months after dose 2 (phase I trial only). Main outcome measures were the change in immunogenicity at each follow-up visit from baseline, measured using HA inhibition (HI) and virus microneutralisation (MN) assays, and the frequency and nature of adverse events (AEs). Computer generated tables were used to randomly allocate treatments; participants and investigators were blinded to treatment allocation. FINDINGS: All formulations were well-tolerated; no unexpected serious adverse events were reported. Two doses of 30 microg or 45 microg H5 HA adjuvanted formulations elicited the highest immune responses, with considerable MN antibody (>or=1:20) persistence up to 6 months post-vaccination. The 7.5 and 15 microg formulations (+/-adjuvant) were less immunogenic than the higher dose formulations; HI and MN antibody titres decreased to near pre-vaccination levels at 6 months but were restored to post-dose 2 levels after the booster dose. Immune responses in the phase I trial demonstrated modest levels of cross-protective MN antibodies against two currently circulating, distinct clade 2 H5N1 strains. INTERPRETATION: Two doses of prototype 30 microg or 45 microg aluminium-adjuvanted, clade 1 H5N1 vaccines were immunogenic and well-tolerated with considerable 6-month antibody persistence. The prototype H5N1 vaccine also elicited modest levels of cross-protective MN antibodies against variant clade 2 H5N1 strains [ClinicalTrials.gov identifiers: NCT00136331, NCT00320346; FUNDING: CSL Limited, Australia].