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.


RESULTS
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.


CONCLUSIONS
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;


BACKGROUND
CSL Limited, Australia].
Nolan
Terry M
TM
Murdoch Childrens Research Institute, and the Melbourne School of Population Health, University of Melbourne, Carlton, Victoria, Australia. t.nolan@unimelb.edu.au
Richmond
Peter C
PC
Skeljo
Maryanne V
MV
Pearce
Georgina
G
Hartel
Gunter
G
Formica
Neil T
NT
Höschler
Katja
K
Bennet
Jillian
J
Ryan
David
D
Papanaoum
Kelly
K
Basser
Russell L
RL
Zambon
Maria C
MC
D000276:Adjuvants, Immunologic / Q000008:administration & dosage; D000293:Adolescent; D000328:Adult; D000534:Alum Compounds / Q000008:administration & dosage / Q000494:pharmacology; D000914:Antibodies, Viral / Q000097:blood; D001315:Australia; D005260:Female; D006385:Hemagglutination Inhibition Tests; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology; D006801:Humans; D007117:Immunization, Secondary; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000009:adverse effects* / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D009500:Neutralization Tests; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology; D022223:Vaccines, Subunit / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology
D000276:Adjuvants, Immunologic; D000534:Alum Compounds; D000914:Antibodies, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated; D022223:Vaccines, Subunit; C483468:hemagglutinin, human influenza A virus; C041524:aluminum sulfate