The H9N2 influenza strain has infected a small number of people and may have the potential to cause a human pandemic.
The 96-patient study explored the safety and immunogenicity of four different doses of the investigational vaccine with and without Chiron’s adjuvant MF59. An adjuvant is a substance that is added to a vaccine to boost the body’s immune response to the vaccine’s antigen.
All vaccine formulations containing the adjuvant MF59 proved highly immunogenic, inducing antibody levels believed to confer protection against the influenza strain. The lowest dose contained 3.75 micrograms of antigen per dose, a quarter of the dose used in seasonal influenza vaccines.
In marked contrast, the unadjuvanted vaccine induced significantly lower antibody titers and did not reach levels achieved by the adjuvanted vaccine following any of the antigen doses tested, which ranged from 3.75 to 30 micrograms.
“Adjuvants could be an important means of improving the immune response to potential pandemic strains and allow us to stretch production capacity,” added Dr Walter Orenstein, professor of medicine of pediatrics and associate director of the Emory Vaccine Center in Atlanta, Georgia.