Get the tissues and chicken noodle soup ready. The US Centers for Disease Control and Preventions (CDC) has recently announced that they expect this flu season to be a rough one, with the flu vaccine facing a reduced ability to prevent infections of the ever-changing virus.

That's because there are reportedly more drift variants of the influenza A H3N2 virus this year, this being the strain predominantly behind infection for this season.

"It's too early to say for sure that this will be a severe flu season, but Americans should be prepared," CDC director Tom Frieden said in a statement. "We can save lives with a three-pronged effort to fight the flu: vaccination, prompt treatment for people at high risk of complications, and preventive health measures, such as staying home when you're sick, to reduce flu spread."

So what's the problem? Because of how frequently the flu virus mutates, vaccinations have never been a surefire way to stop infections. Instead, they are used as an supplement to help back up the human immune system and clean hygiene - which are often strong enough to resist infection in healthy adults. At its best, a flu vaccine has an 80 percent prevention rate, according to the CDC, but as a season goes on, that rate can fluctuate. Between 2007 and 2008 - another drift variant year for H3N2 prevalence - the vaccine was only about 42 percent effective.  This season may be no different.

"While the vaccine's ability to protect against drifted H3N2 viruses this season may be reduced, we are still strongly recommending vaccination," added Joseph Bresee, chief of the Influenza Epidemiology and Prevention Branch at CDC. "Vaccination has been found to provide some protection against drifted viruses in past seasons. Also, vaccination will offer protection against other flu viruses that may become more common later in the season."

The very young and very old are generally most at risk of infection and hospitalization from the flu virus. However, the illness can be unpredictable. Last year's predominant flu strain, a mutated H1N1 virus, was found to target people who were both young and obese the most, while largely leaving healthy seniors alone.

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