In earlier years, only one or two strains are changed each year, and flu vaccine manufacturers take long time to complete the entire production process for the 100 million doses due by the fall.
However, the health authorities are concerned about the production of a strain called Brisbane/10. It takes time to grow in the laboratory thus complicating already laborious vaccine production.
The World Health Organization announced last week its recommendations for next year's flu vaccine, which includes protection against the H3N2 strain and other strains not in this year's vaccine.
Keeping track with the WHO recommendation, the FDA panel on Thursday included Brisbane/10, a version of the H3N2 flu; a second new Type A strain known as H1N1/Brisbane/59, and a newer Type B/Florida strain.
The virus strain most common in the United States right now is the influenza A H3N2 strain, and it's a strain not included in this year's vaccine.
The flu vaccine should be reintroduced every year to keep up with the ever-evolving influenza virus. The flu season peaked in mid-January as some new strains arrived and the Centers for Disease Control and Prevention (CDC) found the vaccine is a good match for only about 40 percent of the virus now spreading in the U.S.
Many of the infections are being caused by strains not covered by this year's vaccine. And some strains are becoming resistant to a common antiviral medication.
According to CDC, this year's flu vaccine doesn't match two of the three strains of influenza currently circulating in the United States. Also, this year's vaccine is not well-matched against influenza type B.
An estimated 5 percent to 20 percent of the U.S. population suffers from the flu each year. More than 200,000 people are hospitalized from flu complications, and about 36,000 people die from the disease.
