You'll only need a single shot of influenza vaccine this year to protect against three strains of the flu, including the H1N1 virus that sparked the 2009 pandemic.

The federal Food and Drug Administration today approved vaccines for the 2010-2011 flu season, and they include drugs to protect against H1N1, another strain of influenza A, Perth, and a strain of influenza B, Brisbane.

The news comes as the Centers for Disease Control and Prevention officials have announced expanded recommendations that urge everyone older than six months get a seasonal flu shot.

Manufacturers expect to produce about 170 million doses of the new seasonal vaccine, which is higher than the 100 million doses offered in a typical flu season, but lower than the nearly 200 million doses of H1N1 vaccine ordered by the government last year, said Tom Skinner, a spokesman for the Centers for Disease Control and Prevention.

Vaccine came too late
Last year, the onset of the H1N1 outbreak started too late to include with production of regular seasonal vaccine, so people needed two separate doses to be protected. This year, just one shot is required. It typically takes six months for flu shots to become available.

"The best way to protect yourself and your family against influenza is to get vaccinated every year," said Dr. Karen Midthun, acting director of the FDA's Center for Biologics Evaluation and Research. "The availability of a new seasonal flu vaccine each year is an important tool in the prevention of influenza-related illnesses and death."

Matching flu vaccines to expected illnesses can be tricky, FDA officials said. There's always a chance that the actual viruses will be different than the ones targeted by the vaccines. Even if they don't match exactly, the vaccine can reduce the chance and the severity of illness, officials noted.

Last year, the government ordered nearly 200 million doses of vaccine to prevent H1N1, also dubbed swine flu, but had to destroy about 40 million doses that expired after demand waned.
Cost of the incinerated vaccine was about $260 million, according to the Associated Press.

"It was just a matter of circumstance that resulted in flu activity peaking before vaccine was widely available," said Skinner, of the CDC.

Between 5 percent and 20 percent of the U.S. population comes down with flu in a typical year, leading to more than 200,000 hospitalizations and about 36,000 deaths. Swine flu turned out to be less deadly than first feared, with about 12,000 deaths.