Safety and immunogenicity of whole-virus, alum-adjuvanted whole-virus, virosomal, and whole-virus intradermal influenza A/H9N2 vaccine formulations.
Avian influenza H9N2 viruses are considered as a pandemic threat. We assessed the safety and immunogenicity of fourteen H9N2 vaccine formulations. A randomized, phase I trial was done in 353 adults, aged 18-82 years. Subjects received two doses of A/Hong Kong/1073/99 (H9N2) whole-virus, alum-adjuvanted whole-virus, virosomal, or intradermal whole-virus vaccine at four doses (1.7, 5, 15 or 45 microg haemagglutinin). Sera were obtained before and three weeks after each vaccination (days 0, 21, and 42) for haemagglutination-inhibition (HAI) and neutralization assays. All formulations were well tolerated. Pre-vaccination sera from subjects aged below or above 40 years had baseline antibody to H9N2 in 1% and 16% of samples. Compared to intramuscular whole-virus vaccine, alum-adjuvanted vaccine was more immunogenic, intradermal vaccine was comparable, and virosomal vaccine less immunogenic. Among subjects under 40 years, two doses (45, 15, and 5 microg) of alum-adjuvanted vaccine achieved seroprotective HAI titres in 50%, 41%, and 39% respectively, and neutralization seroconversions in 83%, 82%, and 78% of recipients. Among subjects over 40 years, one dose (45, 15, and 5 microg) of alum-adjuvanted vaccine achieved seroprotective HAI titres in 50%, 25% and 0% respectively, and neutralization seroconversions in 88%, 63% and 63% of recipients. Among immunologically naive subjects under 40 years, two doses of vaccine are required and alum-adjuvanted vaccines were most immunogenic. Among immunologically primed subjects over 40 years, one dose of whole-virus or alum-adjuvanted vaccine induced immune responses; the second dose provided less additional benefit. However, no vaccine formulation satisfied all European regulatory criteria for pandemic vaccines.
Infectious Diseases Unit, University Hospitals Leicester, Leicester, LE1 5WW, UK. karlgnicholson@doctors.org.uk
Karl G
KG
Nicholson
Catherine I
CI
Thompson
Jaco M
JM
Klap
John M
JM
Wood
Sally
S
Batham
Robert W
RW
Newman
Robert
R
Mischler
Maria C
MC
Zambon
Iain
I
Stephenson
D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000534:Alum Compounds / Q000494:pharmacology; D000914:Antibodies, Viral / Q000097:blood; D000917:Antibody Formation; D005260:Female; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007117:Immunization, Secondary; D053127:Influenza A Virus, H9N2 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000009:adverse effects / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology / Q000517:prevention & control*; D007271:Injections, Intradermal; D008297:Male; D008875:Middle Aged; D009500:Neutralization Tests; D022721:Vaccines, Virosome / Q000276:immunology; D055815:Young Adult
D000276:Adjuvants, Immunologic; D000534:Alum Compounds; D000914:Antibodies, Viral; D007252:Influenza Vaccines; D022721:Vaccines, Virosome