Amid the most severe influenza season in more than a decade, federal health officials on Wednesday approved a next-generation, insect-based flu vaccine that sidesteps the thorniest parts of production -- and will be used immediately in people willing to test it.
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Food and Drug Administration officials gave the nod to Flublok, the first vaccine made by injecting flu genes into an insect virus and growing it in caterpillar cells. That means, unlike current vaccines, it does not require the whole flu virus grown in chicken eggs for production.
About 150,000 doses of the vaccine have been produced and will be distributed by mid-February to people with egg allergies and others who are unable to receive current flu vaccines, said Manon Cox, president and CEO of Protein Sciences Corp., Meriden, Conn., firm that came up with the new process. It's approved for use in adults ages 18 to 49.
"We've collected names and we'll see what we can do to help," said Cox.
Flublok's novel manufacturing technology allows for production of large quantities of the flu virus protein known as hemagglutinin or HA, FDA officials said in a statement. That is the active ingredient in all inactivated flu vaccines required for entry of the virus into cells in the body. Most of the antibodies that prevent infection are directed against HA, FDA noted.
"This approval represents a technology advance in the manufacturing of an influenza vaccine," said Dr. Karen Midthun, director of the FDA's Center for Biologics Evaluation and Research. "The new technology offers the potential for faster start-up of the vaccine manufacturing process in the event of a pandemic, because it is not dependent on an egg supply or on availability of the influenza virus."
In vaccines produced now, the virus must be isolated from patients' blood, purified and injected into specific kinds of chicken eggs to grow. The Flublok technology avoids those time-consuming steps in a process that will be faster, easier to control and easier to scale up in an emergency.
Flublok contains three full-length recombinant HA proteins to help protect against three strains of the flu including two influenza A viruses, H1N1 and H3N2, and one strain of influenza B. Flublok has a shelf life of 16 weeks from the date of manufacture.
The vaccine was tested in about 2,500 people who were inoculated with Flublok. FDA officials rejected the company's first pitch for approval in 2009, asking for more safety data. In new users, the most commonly reported adverse events included pain at the injection site, headache, fatigue and muscle aches, side-effects that also are common in egg-based vaccines.
The U.S. is in the midst of a moderate to severe flu outbreak, with deaths reaching epidemic levels and activity widespread across 90 percent of the country, according to the Centers for Disease Control and Prevention.
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This story originally appeared on NBCNews.com.