GSK's flu vacc protects 80% of trial subjects

UK drug major GlaxoSmithKline has reported headline data showing that its H5N1 pandemic flu vaccine achieved a high immune response against a low dose of antigen. The vaccine, which uses a proprietary adjuvant, enabled over 80% of subjects who received 3.8mcg of antigen to demonstrate a strong seroprotective immune response.

According to the London-headquartered firm, this level of seroprotection meets or exceeds target criteria set by regulatory agencies for registration of influenza vaccines. Efficacy results at these levels of antigen dosage have also not been reported for any other H5N1 vaccine in development to date, including those using other adjuvants such as alum. Jean-Paul Garnier, GSK's chief executive, noted that "all being well, we expect to make regulatory filings for the vaccine in the coming months."

The results were based on an interim analysis of a clinical trial conducted in Belgium, which involved 400 healthy adults aged 18-60 years. The vaccine tested was produced from inactivated H5N1 virus and contained GSK's novel, proprietary adjuvant. In this study, immune response was defined as the increase in the number of antibodies an individual produced in response to the vaccine. Levels of antibody protection were established through measurement of hemagglutination inhibition, which is a standard efficacy measure used in the evaluation of influenza vaccines, and GSK defined its endpoint of strong seroprotection as an HI titer of greater than 40.