GlaxoSmithKline (NYSE: GSK) will soon have another weapon to combat flu.

On Friday, GSK said the U.S. Food and Drug Administration had approved its Flulaval Quadrivalent influenza virus vaccine for use by patients age 3 and over.

Fluarix Quadrivalent was approved by the FDA last December and its now shipping.

“Since the late 1980s, public-health authorities have known that four primary influenza strains circulate each year causing the majority of influenza illness, but the influenza vaccines used for the past thirty years only covered against three strains”, said Dr. Leonard Friedland, director of Scientific Affairs and Public Health at GSK Vaccines North America. “With this limitation, global influenza experts have had to make a difficult determination around the strains each season to cover, and in six of the past 11 influenza seasons (2001-2012), one of the predominant strains was not included in the season’s influenza vaccines. Trivalent vaccines do reduce influenza risk even in years when a vaccine strain-mismatch occurs, though quadrivalent influenza vaccines are the important next step in broadening strain coverage.”

Flurarix is a quadrivalent vaccine; the injectable vaccine provides immunity against two strains each of influenza virus types A and B. The 2013-2014 flu season will be GSK’s first selling a vaccine that protects against more than three strains of flu.

The strains that cause seasonal influenza are classified into two strains, A and B. Most of the current vaccines protect against three strains, two A strains and the B strain expected to be predominant in the coming flu season. But scientists have noted since the late 1980s that two B virus lineage strains circulate to varying degrees from year to year making it difficult to predict which one will be most likely to cause illness.

“Fluarix Quadrivalent addresses this by protecting against both B strains.” Dr. Leonard Friedland, VP, Scientific Affairs and Public Policy, GSK Vaccines, North America, said in a statement.

GSK received FDA approval on Fluarix last year. The latest approval clears the way for GSK to ship Fluarix to those U.S. health care providers who have placed orders for it. The Centers for Disease Control and Prevention has ordered more than 4 million doses of Fluarix making it the largest order of the vaccine. The CDC each each year purchases large quantities of vaccines from various drug companies.

Britain-based GSK, which operates its U.S. headquarters in Research Triangle Park, estimates it will provide as many as 10 million doses of Fluarix in the United States this flu season.

[GSK ARCHIVE: Check out more than a decade of GSK stories as reported in WRAL Tech Wire.]