Flu Shot Only Helps About 40% of the Time
02/08 | The flu season is getting worse. United States health officials say it's because the flu vaccine doesn't protect against most of the spreading flu bugs.
Officials at the U.S. Centers for Disease Control and Prevention said that the flu shot is a good match for only about 40 percent of this year's flu viruses.
And the bad news just keeps getting worse. At the beginning of February, the CDC said the vaccine was protective against roughly half the circulating strains, and now they have revised that figure to 40%. In good years, the vaccine can fend off 70 to 90 percent of flu bugs.
Infections from an unexpected strain have been booming, and now are the main agent behind most of the nation's lab-confirmed flu cases.
"Every area of the country is experiencing lots of flu right now," said Dr. Joe Bresee, the CDC's chief of influenza epidemiology.
Last week, 44 states reported widespread flu activity, up from 31 the week before. The number children who have died from the flu has risen to 10 since the flu season's official Sept. 30 start.
Early February is the time of year when flu cases tend to peak, so the numbers are not particularly cause to panic. The 10 pediatric deaths, though tragic, are about the same number as was reported at this time in the last two flu seasons, Bresee said.
The biggest surprise has been how poorly the vaccine has performed.
Experts try to predict which strains of flu will circulate each winter. They develop an appropriate vaccine for the following season.
It's all guesswork, but they've had a pretty good run: in 16 of the last 19 flu seasons the vaccines have been a good match.
But not this year. It's a poor defense against the circulating viruses. In particular, it is ineffective against the Type A H3N2/Brisbane-like strain that now accounts for the largest portion of lab-confirmed cases.
Over the years, the H3N2 flu has tended to cause more deaths.
This week, the World Health Organization took the unusual step of recommending that next season's flu vaccine have a completely different makeup from this year's. The U.S. Food and Drug Administration is expected to make its decision about the U.S. vaccine this week.
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