FDA approves quadrivalent seasonal flu vaccine

Beginning next year, health officials may be allowed to include two influenza B strains in the seasonal flu vaccine.

The U.S. Food and Drug Administration recently approved FluMist Quadrivalent, a four-pronged influenza vaccine that contains both of the distinct lineages of influenza B in circulation, according to Nature.

The new quadrivalent vaccine could be administered to people aged two to 49. In three separate clinical trials involving 4,000 subjects, the vaccine was shown to be capable of promoting comparable immune responses to the existing three-strain FluMist.

In recent years, predictions about which influenza B strain would be more prevalent in the United States have only been correct approximately half the time.

"Our ability to predict which of these strains will circulate has not been great," Ruth Karron, the director of the Center for Immunization Research at the Johns Hopkins Bloomberg School of Public Health, said, Nature reports. "We might as well have tossed a coin."

MedImmune, the Maryland-based subsidiary of AstraZeneca that produces FluMist, recently announced that it plans to stop offering the current trivalent vaccine starting in the 2013-2014 season. The company plans to file for European Union regulatory acceptance later this year.

"It's a significant advance," Robert Belshe, of St. Louis University, a leader of the pediatric trial involving FluMist, said, Nature reports. "It takes the guessing work out of the B component."