The U.S. Food and Drug Administration has approved the first adjuvanted vaccine for the prevention of H5N1 avian influenza. The vaccine, Influenza A (H5N1) Virus Monovalent Vaccine, Adjuvanted, is for use in people 18 years of age and older who are at increased risk of exposure to the H5N1 influenza virus.
Avian influenza A viruses typically do not infect people, however some viruses, such as H5N1, have caused serious illness and death in people outside of the U.S., mostly among people who have been in close contact with infected poultry. When people do become infected with H5N1, about 60 percent die, according to the World Health Organization. H5N1 is an influenza virus with pandemic potential because it continues to infect wild birds with occasional outbreaks of influenza disease in poultry populations, and most humans have no immunity to it.
"This vaccine could be used in the event that the H5N1 avian influenza virus develops the capability to spread efficiently from human to human, resulting in the rapid spread of disease across the globe," said Karen Midthun, M.D., director of the FDA's Center for Biologics Evaluation and Research. "Vaccines are critical to protecting public health by helping to counter the transmission of influenza disease during a pandemic."
The H5N1 avian influenza vaccine is not intended for commercial availability. The U.S. Department of Health and Human Services has purchased the vaccine from the manufacturer, ID Biomedical Corporation of Quebec (a subsidiary of GlaxoSmithKline Biologicals), for inclusion within the national stockpile for distribution by public health officials if needed.
The vaccine is made using an egg-based manufacturing process, which is also used for ID Biomedical Corporation's seasonal influenza vaccine, FluLaval. It contains the adjuvant AS03, an oil-in-water emulsion. An adjuvant is a substance incorporated into some vaccines to enhance or direct the immune response of the vaccinated individual. The adjuvant makes it possible to use a small amount of influenza protein per dose of vaccine to elicit the desired immune response in an individual to prevent influenza disease. Reducing the amount of influenza protein per dose helps to increase the total number of doses of a safe and effective vaccine available for the public during a pandemic.
The H5N1 component and the AS03 adjuvant component are supplied in two separate vials, which must be combined prior to use. The vaccine is administered via intramuscular injection in two doses, 21 days apart.
The evaluation of safety compared approximately 3,400 adults 18 years of age and older who received the vaccine to about 1,100 adults who received placebo in a multi-center study. The most common side effect reported during the clinical studies among the vaccine recipients was injection site pain. Muscle aches, headache, fatigue and injection site redness and swelling were also common. To determine how well the vaccine works, the immune response was evaluated in about 2,000 of the vaccinated adults. The results showed that 91 percent of individuals between the ages of 18 and 64 years and 74 percent of individuals 65 years and older who received the two-dose regimen developed antibodies at a level that is expected to reduce the risk of getting influenza.
The manufacturer will collaborate with the FDA and other U.S. governmental agencies on plans to collect additional safety and effectiveness data through U.S. government-sponsored studies of the vaccine, in the event that it is used during an H5N1 influenza virus pandemic.