There's bad news about this year's flu vaccine.
The most common type of flu being seen in the United States is influenza A H3N2, the same severe strain that dominated last flu season.
And in Australia, where the winter flu season has just wrapped up, this season's vaccine was only about 10 percent effective against the H3N2 strain.
"Our vaccine is the same as the one used in Australia," said Lynnette Brammer, an epidemiologist in the influenza division of the U.S. Centers for Disease Control and Prevention. "The vaccine doesn't work as well for H3N2 viruses in general."
But she added that a 10 percent effectiveness rate still seems a bit low. Last year, a similar vaccine was 43 percent effective against the H3N2 virus and 48 percent effective overall, according to the CDC.
And Brammer added that other types of flu are circulating, including influenza A H1N1 and a couple of influenza B viruses. The flu vaccine is very effective against these, she noted.
Despite its low effectiveness, Brammer urges everyone aged 6 months and older to get a flu shot.
"The vaccine doesn't work as well for H3N2 as we would like, but does work for some and it may provide partial protection. And there are a lot of H1N1 and B viruses out there," Brammer said.
The flu is being seen throughout the country and is very active in the South and New England, but it's not too late to get vaccinated, she said.
H3N2 can be particularly hard on the elderly and the very young.
Each year, hundreds of thousands Americans are hospitalized for flu and thousands die, according to the CDC.
If you do catch the flu, Brammer suggests taking antivirals such as Tamiflu to reduce the number of days you are sick. The drug works best when taken right when you get sick, so seeing your doctor early is a good move, she said.
The CDC also advises people to wash their hands often to prevent spreading flu, and to stay home if they're sick so they won't spread it to others.
It's too early to tell if H3N2 will continue to be the predominant strain or whether H1N1 will surpass it, Brammer said.
Usually, a H3N2 portends a severe flu year, but mild H3N2 years have also occurred, she said.
"The most predictable thing about flu is that it's unpredictable," Brammer said.
Dr. Marc Siegel is an infectious diseases expert from NYU Langone Medical Center in New York City. "It's a good guess that H3N2 will predominate, and that's worrisome," he said.
Still, "I believe it's worth getting the vaccine," Siegel said. "I believe there is a booster effect, although I can't prove that."
Having been vaccinated once against the various strains of the virus makes being vaccinated again even more effective, he explained.
Siegel added that he worries that "this could be a very severe flu season."
Visit the U.S. Centers for Disease Control and Prevention for more on the flu.
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