3 New Strains of Flu Vaccine for Next Season

The FDA announced that for the coming flu season, the flu shot will be made up of three new flu strains: 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 reason is that this year's vaccine has proven to be only 40 percent effective, rather than the 70 percent to 90 percent that is more usual.

Since it takes a long time to create a flu vaccine, scientists have to make their best risk estimate of what next season's predominant viruses are going to be nine months in advance. Most times, they get it right, but sometimes not, like this year.