FDA panel backs avian flu vaccine for adults

A Food and Drug Administration advisory panel gave its unanimous support to vaccine designated for a national stockpile, where it would be reserved for use during an avian influenza pandemic or outbreak.

The FDA’s Vaccines and Related Biological Products Advisory Committee voted 14-0 that the influenza A (H5N 1) virus monovalent vaccine should be approved based on the safety and immune responses seen in clinical studies.

With the US government to develop the vaccine, which contains an antigen-sparing adjuvant that boosts the immune response, if licensed, it will be deposited in the US Strategic National Stockpile and owned by the US government, which would control the distribution.

The advisory committee agreed that immunogenicity and safety data on the “Q-pan H5Nl” vaccine support licensure for use in adults at increased risk of exposure or during a pandemic. The proposed indication is for the prevention of disease in persons 18 years of age and older at increased risk of exposure to the influenza, a virus H5Nl subtype contained in the vaccine.” The vaccine is administered in two doses about 21 days apart.

Mortality from the infection is highest among children and young adults. GSK is conducting studies in children aged 17 months and older, with plans to expand the approval.

The influenza A (H5Nl) virus is highly pathogenic, contagious, and deadly among birds, particularly domestic poultry. There are sporadic outbreaks in humans; since November 2003, there have been 608 confirmed cases in 15 countries — mostly in Asia — with a high (59%) mortality rate, according to the Centers for Disease Control and Prevention.

The vaccine was the focus of two pivotal studies of 5,214 patients, including 3,574 who received the Q-Pan H5Nl. In a phase III study comparing the vaccine with a saline placebo, seroconversion rates 42 days after the second dose were 90% among those aged 18-64 years and 74% of those over age 64 years. This exceeded FDA criteria for immunogenicity for a vaccine.

The vaccine is being considered for an accelerated approval, with the immune responses to the vaccine being considered a surrogate for clinical effectiveness. Moreover, the vaccine is manufactured using the same process as GSK’s seasonal influenza vaccine, Flu Laval; full approval is dependent on postapproval studies confirming clinical benefit.