HealthDay News — The FDA has approved the first adjuvanted vaccine to prevent against avian influenza A H5N1  in adults at greater-than-average risk of exposure.

The influenza A (H5N1) virus monovalent vaccine is intended for people aged 18 years and older and is designed to be administered in two doses given three weeks apart. The vaccine is not intended for commercial distribution, but to supplement the national stockpile of influenza vaccines, the FDA said.

Although most strains of avian influenza do not infect people, the H5N1 virus has caused “serious illness and death in people outside of the United States, mostly among people who have been in close contact with infected and ill poultry,” the agency said in a news release announcing the approval.

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Among people who have become infected with H5N1, mortality is about 60%, according to WHO. Health officials have determined the H5N1 strain of influenza has “pandemic potential” because it continues to affect wild birds and poultry populations, and most humans have no immunity to it.

The shot has been developed “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 the disease across the globe,” the FDA added.

Clinical testing involving some 3,400 adults who received the vaccine and 1,100 who received placebo. An analysis of immune response in 2,000 vaccinated participants indicated that 91% of those aged 18 to 64 years and 74% of those aged 65 years and older achieved a protective antibody response with the two-dose regimen. The most common vaccine side effects included injection-site pain and swelling, muscle aches, headache and fatigue.

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