This winter’s flu season may be worse than anticipated, said officials of the U.S. Centers for Disease Control and Prevention last week, and the vaccine less effective.

“The flu season is beginning and we are seeing some things that are concerning and that led us to issue a health advisory … ” said Dr. Tom Frieden, CDC director during a Dec. 4 press conference. “One thing to understand about flu always is that it is unpredictable.”

The concern arose because the most common influenza viruses seen this fall are slightly different than the strains, which this season’s flu vaccine targets. Influenza A, or H3N2 viruses, is dominating the influenza test results throughout the nation.

In years when H3 viruses predominate, Frieden reported, “we tend to have seasons that are the worst flu years … The rate of hospitalization and death can be twice as high as or more than in flu season when H3 doesn’t predominate.”

The virulence of H3 viruses is exacerbated because in March when decisions about which influenza viral strains the vaccine should target were made, these H3 viruses were a smaller portion of the circulating flu. Consequently, the vaccine does not include antigens for these particular H3 strains.

Since September, CDC has identified these H3 viruses, which were not part of the vaccine formulation, in about half the influenza analyses. Apparently, the virus’ genetic component has “drifted” since March, which is the reason the CDC has issued this alert.

Regardless of whether one has been vaccinated, Frieden urged individuals to use and doctors to prescribe antivirals. “Vaccinations prevent flu, but antivirals are an important second line of defense to treat the flu,” Frieden emphasized.

People with a high risk for flu severity or complications should seek antivirals. Those at high risk include children younger than age 5 (especially those younger than age 2); adults 65 years and older; pregnant women; and people with certain chronic health conditions such as asthma, diabetes, heart or lung disease, or kidney disease.

Frieden advised that the CDC continues to recommend vaccination first, then antiviral medication. At the first sign of flu, high-risk individuals should see a doctor.

Two FDA-approved drugs recommended for use in the U.S. during this season are Tamiflu (oseltamivir) and Relenza (zanamivir). Treatment with antiviral drugs works best when they are begun within 48 hours of getting sick, but they can still be helpful in some patients when given later in the course of the illness.

The antivirals can make the difference between a severe flu or a mild one, but research indicates that patients tend to have one less day of flu. “These are miracle drugs,” Frieden emphasized.

Already this flu year, five children have died. Four of those were infected with influenza A and three were confirmed H3 viruses, according to Dr. Joe Breese, CDC’s chief of the Influenza Epidemiology and Prevention Branch.



Flu vaccine urged

Many people fear the flu vaccine because they believe they can catch the flu from the vaccine. But there are no live virus in the vaccine.

According to the CDC, “The flu shot contains inactivated (killed) flu viruses that cannot cause illness.”

Flu symptoms, such as soreness, redness, and swelling at the injection site; fainting, mainly in adolescents; headaches; fever; or nausea may appear and last about a day or two.