The U.S. Food and Drug Administration has approved the first adjuvanted vaccine for H5N1 influenza, also known as the avian or bird flu. The vaccine, which won't be available for commercial use and does not have a trade name in the U.S., will be distributed by public health officials if needed during an outbreak, the FDA stated in a news release.

"This vaccine could be used in the event that the H5N1 avian influenza virus develops the capability to spread efficiently from human to human," Dr. Karen Midthun, director of the Center for Biologics Evaluation and Research (CBER) at the FDA, said in a news release. “Vaccines are critical to protecting public health by helping to counter the transmission of influenza disease during a pandemic.”

The bird flu virus can be transmitted to humans through exposure to dead animals or infected environments. According to the World Health Organization (WHO), since 2003 there have been a total of 641 human cases of the bird flu, and 380 deaths — most occurring in countries such as Azerbaijan, Viet Nam, Egypt, and Indonesia. The vaccine would be for people over the age of 18, who may be at risk of exposure to the disease.

According to the FDA, the vaccine was evaluated in over 3,000 adults over the age of 18 and compared to 1,100 adults who received a placebo. The FDA found that 91 percent of those who were between 18 and 64 were able to develop antibodies to the virus, after receiving a two-dose regimen of the vaccine.

Earlier this month, Taiwanese scientists investigated the first case of a human infected with influenza A H6N1, which was a strain that was only found in birds previously.

Safety Of Adjuvants

According to the Centers for Disease Control and Prevention (CDC), a vaccine adjuvant is a substance added to the vaccine that helps improve the body’s immune response to the vaccine. Sometimes aluminum gels or salts are used in the vaccine. Adjuvant aluminums have been used since the 1930s, in vaccines for hepatitis A and B, diphtheria, and HPV. The vaccine for the avian influenza uses an oil-in-water emulsion, made with an egg-based process.

The U.S. has been relatively cautious about the use of adjuvants compared to other countries. Pandemrix, for example, is a swine flu vaccine with an adjuvant developed by GlaxoSmithKline that was patented in 2006. However, Pandemrix was linked to narcolepsy, a neurological disorder that causes disrupted sleep. The Swedish Medical Products Agency (MPA) led an investigation in 2010, finding that children had an increased risk to develop narcolepsy if they had taken the adjuvant. Pandermix was not approved by the FDA, and most health experts believed that traditional, non-adjuvanted H1N1 (swine flu) vaccines were good enough. In a statement made in the spring of this year, the Centers for Disease Control and Prevention stated that Pandemrix was never licensed for use in the U.S., and in fact, no adjuvanted flu vaccines were licensed in the U.S. until now.

Though adjuvants have been used for decades for diseases like diptheria and tetanus, new and untested adjuvants are being developed, leading to some concerns about safety. While the use of adjuvants have been controversial, Professor David Salisbury, head of immunization at the U.K. Department of Health, told the Telegraph that “One of the advanages with adjuvanted vaccines is their ability to protect against drifted strains. It opens the door for a whole new strategy in dealing with flu.”