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FDA Approves New Flublok Flu Vaccine

, by Reilly O'Neal

The U.S. Food and Drug Administration (FDA) yesterday approved the influenza vaccine Flublok for use in adults age 19 to 49. (Approval for all people over 18 years of age is anticipated later this year, according to a press release from manufacturer Protein Sciences.)

So what makes this new flu shot different from existing vaccines?

Perhaps most significant for HIV-positive people, Flublok contains triple the standard dose of laboratory-produced viral proteins called antigens, the vaccine ingredient that triggers an immune response and “teaches” the body to recognize and fight off flu viruses. As at least one recent study has suggested, high-dose flu vaccines may better protect people with weakened immune systems, including those living with HIV.

Second, production of the vaccine does not involve live flu viruses; rather, Flublok is made using hemagglutinin (HA), an influenza virus protein that allows the virus to enter cells. “The majority of antibodies that prevent influenza virus infection are directed against HA,” according to an FDA press release. This feature makes approval of the new vaccine significant for people with HIV, who are advised not to receive the live-virus-containing flu vaccine FluMist (administered as a nasal spray).

Third, Flublok is manufactured without the use of eggs—good news for people whose egg allergy makes flu shots off limits and leaves them vulnerable to infection. Instead, the new vaccine is produced using an “insect virus expression system.” In short, scientists take a virus that causes infection in insects and genetically modify it to produce large quantities of the hemagglutinin protein that gives the new vaccine its oomph.

This manufacturing approach represents a breakthrough in vaccine production. “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,” explains Karen Midthun, MD, director of the FDA’s Center for Biologics Evaluation and Research, in the FDA press release.

Great! But how well does it work?

“The effectiveness of Flublok was evaluated in a study conducted at various sites in the United States that compared the use of Flublok in about 2,300 people to a placebo that was given to a control group of similar size,” the press release continues. “Flublok was about 44.6 percent effective against all circulating influenza strains, not just the strains that matched the strains included in the vaccine.”

Let’s back up a little: Because flu viruses change over time, every year public health organizations like the FDA, the Centers for Disease Control and Prevention, and the World health Organization look at worldwide data on flu infections and try to pinpoint the viral strains (subtypes of the main types of flu viruses) that are expected to cause the most illness in the coming flu season. (In the U.S., flu season typically begins in the fall and peaks in January or February, but it can last into mid-spring.)

Armed with this knowledge, manufacturers produce vaccines that they anticipate will best “match” the flu virus strains circulating and causing illness in the coming flu season—but some strains may not be covered by the shots and can still cause infection. Flublok’s ability to reduce the risk of infection with all circulating strains (in one study, at least) is a definite plus.

How can you get this new flu shot?

“Flublok will be widely available for the 2013–2014 influenza season and is available in limited supply for the current season,” states the Protein Sciences’ press release. If you haven’t already had your flu shot (it’s not too late!) and are interested in the Flublok vaccine, check with your medical provider and/or your local pharmacy for news of any supplies near you. [UPDATE 2/20/13: The manufacturer’s “Flublock Finder” page listed two Connecticut walk-in clinics at the time of this writing; check back for updates.]

People with HIV are at higher risk for flu infection and for more severe (even life-threatening) symptoms and complications—but again, it’s not too late to get your “traditional” flu shot, and there are additional ways to protect yourself from flu. See the related posts listed below for more resources to help you fight the flu and stay well this season.

Selected Sources

FDA. FDA approves new seasonal influenza vaccine made using novel technology. Press release. January 16, 2013. 

McKittrick, N. and others. Improved immunogenicity with high-dose seasonal influenza vaccine in HIV-infected persons: a single-center, parallel, randomized trial. Annals of Internal Medicine 158(1):19–26. January 1, 2013.

Protein Sciences Corporation. U.S. FDA Approves Flublok, the World’s First Recombinant, Highly Purified, Egg-Free Influenza Vaccine. Press release. January 16, 2013.  


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