By Matt Sloane
WebMD Health News
Dec. 4, 2014 -- Flu season is well underway, and the CDC says the flu shot may not be offering as much protection as experts had hoped.
“So far this season, influenza A -- H3N2 viruses -- have been detected most frequently, and in almost all states,” said CDC Director Thomas Frieden, MD, MPH, in a telebriefing with reporters.
“Unfortunately about half of the viruses in cases that we’ve identified this season are different than the ones that are included in this year’s vaccine. The vaccine won’t protect against these viruses.”
Each year, several months before flu season starts, scientists and vaccine manufacturers from around the globe make an educated guess about which strains of flu will be most common in the coming year, giving them time to make the vaccines before the season begins.
But in some cases, these guesses can be wrong, or viruses can mutate while the vaccine is being made. Even in a “well-matched” flu vaccine year, the vaccine is only 60%-90% effective.
“The flu virus can be unpredictable, and what we’ve seen so far this year is concerning,” Frieden said.
Because vaccines take at least 4 months to make, there is little that can be done to adjust this year’s vaccine.
Flu Hot Spots Cropping Up
There have been over 1,200 confirmed flu cases and 5 deaths, with the most cases being in Alaska, the Pacific Northwest, and the southern central parts of the United States.
Flu seasons where H3 viruses, including this year’s H3N2, are the predominant flu strain tend to be worse, with longer-lasting and more severe illnesses, leading to more hospitalizations and more deaths, Frieden said.
And, he said that of the deaths in children typically seen from the flu, about 90% of those children did not get the vaccine.
Despite a poorly matched vaccine, Frieden says the CDC is still recommending that people get this year’s flu shot.
“In situations such as this, we continue to recommend the vaccine, because although it’s far from perfect, it still offers us the best chance at prevention,” he said.
source : This Year’s Flu Vaccine Less Effective Than Hoped
