New Flu Vaccine: What You Should Know

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(Image credit: Vaccine photo via Shutterstock)

The Food and Drug Administration has approved a new flu vaccine that is made without using chicken eggs. Here's what you need to know about it:

What's different about this vaccine?

Current flu vaccines use whole flu viruses that have been grown in chicken eggs and inactivated. But the new vaccine, called Flublok, uses just a part of the flu virus, a protein called hemagglutinin. This protein is put inside insect cells, which produce massquantities of the protein as they grow. The protein is then purified and put into the vaccine, according to Protein Sciences Corp., the company that makes Flublok.

The proteins in the virus protect against three flu strains: two influenza virus A strains (H1N1 and H3N2), and one influenza virus B strain. It is approved for adults ages 18 to 49.

The vaccine contains three times the active ingredient compared to current vaccines, Protein Sciences said.

Are there fewer side effects?

Flublok causes side effects similar to those caused by egg-based flu vaccines, including pain at the site of injection, headache, fatigue and muscle aches, according to the FDA. The vaccine is given as an injection in the upper arm. [See 8 Strange Signs You're Having an Allergic Reaction.]

How well does it work?

In a study of about 2,300 people who received the actual vaccine, and a similar number who received a placebo, Flublok was 44.6 percent effective against all circulating strains of the flu virus (not just the viruses in the vaccine), the FDA said.

The effectiveness of the yearly flu vaccine depends upon several factors, including how well the flu strains in the vaccine match the strains in circulation. This year's flu vaccine was found to be 62 percent effective.

When will it be available?

The supply for this year is limited, Protein Sciences said, but the company expects the vaccine to be widely available next flu, season, which starts during the fall.

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Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.