A new viral subtype might create more casualties this year because the flu vaccine doesn’t offer strong enough protection against this culprit, says a new advisory from the U.S. Centers for Disease Control and Prevention (CDC), as reported by the New York Times.

Although flu season has just begun, doctors found that of about 1,200 samples tested this year, 91 percent were positive for the H3N2 influenza subtype. According to the CDC, during the years H3 subtypes were common, this led to more hospitalizations and deaths overall.

What’s more, researchers said about half of the H3 subtypes tested—or 45 percent of all flu samples in the country—are of a new H3 subtype that this year’s flu shot does not protect against very well. The new strain didn’t appear in the United States until September. As a result of its late arrival, researchers said, it’s now too late to change this year’s flu vaccine to protect against the new influenza strain.

How does this affect you? The CDC continues to suggest all Americans get flu shots if they haven’t yet. The vaccine still protects against the older H3 strain, influenza B and some H1 flu strains. In addition, the shot may also provide a weak defense against the H3 variation.

Doctors across the country are also being told to prescribe the antivirals Tamiflu or Relenza to those who suffer from asthma, diabetes, or lung or heart problems to boost their ability to fight the flu.

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