Flu Season, and Vaccine, Looking Worse
US Flu Season Getting Worse; Vaccine Only Protects Against 40 Percent of Circulating Flu Bugs
The flu season is getting worse, and U.S. health officials say it's partly because the flu vaccine doesn't protect against most of the spreading flu bugs. The flu shot is a good match for only about 40 percent of this year's flu viruses, officials at the U.S. Centers for Disease Control and Prevention said Friday.
The situation has even deteriorated since last week when the CDC said the vaccine was protective against roughly half the circulating strains. 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, said Dr. Joe Bresee, the CDC's chief of influenza epidemiology.
It's too soon to know whether this will prove to be a bad flu season overall, but it's fair to say a lot of people are suffering at the moment. "Every area of the country is experiencing lots of flu right now," Bresee said.
This week, 44 states reported widespread flu activity, up from 31 last week. The number children who have died from the flu has risen to 10 since the flu season's official Sept. 30 start.
Those numbers aren't considered alarming. Early February is the time of year when flu cases tend to peak. 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.
Each winter, experts try to predict which strains of flu will circulate so they can develop an appropriate vaccine for the following season. They choose three strains two from the Type A family of influenza, and one from Type B.
Usually, the guesswork is pretty good: The vaccines have been a good match in 16 of the last 19 flu seasons, Bresee has said.
But the vaccine's Type B component turned out not to be a good match for the B virus that has been most common this winter. And one of the Type A components turned out to be poorly suited for 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, Bresee said.
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 next week.
H3N2 strains are treatable by Tamiflu and other antiviral drugs, but the other, H1N1 Type A strains are more resistant. Of all flu samples tested this year, 4.6 percent have been resistant to antiviral medications. That's up from fewer than 1 percent last year.
"This represents a real increase in resistance," Bresee said.
On the Net:
The CDC's flu season update: http://www.cdc.gov/mmwr
Copyright 2008 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
Whole new flu vaccine needed next year: WHO
Feb 15, 2008
WASHINGTON (Reuters) - The three most common influenza viruses circulating globally have changed significantly and next year's flu vaccines should be updated, the World Health Organization recommended.
A flu epidemic is well under way in the United States, and the U.S. Centers for Disease Control and Prevention said it had clear indications that the viruses have mutated, making the current vaccine less effective.
WHO said similar reports were coming in globally and it appears next year's vaccine will have to be completely new.
"Forty-four states reported widespread influenza activity," the CDC said in its weekly flu report on Friday. Ten American children have died of flu this season, the CDC said.
About one third of people tested for flu because of their symptoms actually had influenza, the CDC said. Other viruses cause similar symptoms to flu, marked by a sudden onset of fever, muscle aches and weakness.
Influenza viruses mutate constantly. Because of this, experts meet throughout the year to monitor the flu seasons and consider how to formulate the vaccine.
Flu vaccines contain the three most common circulating strains, usually two "A" strains and one "B" strain.
"As in previous years, national control authorities should approve the specific vaccine viruses used in each country," the WHO said.
Even if the flu vaccine is not a perfect match, it can protect people against the most serious effects of the infection. In an average year flu kills between 250,000 and 500,000 people globally.
Four antiviral drugs can help treat a case of the flu, but the WHO said H1N1 viruses in 18 countries had developed mutations that made them resist the effects of the best drug, Tamiflu, or oseltamivir, made by Roche AG and Gilead Sciences.
Resistance to the older drugs, amantadine and rimantadine, is now so widespread that their use is no longer recommended.
Companies usually begin the process of making new flu vaccines several months before the new flu season starts. Flu vaccines are made using a time-consuming process that involves chicken eggs.
WHO starts the process of helping advise companies -- and the governments that buy their vaccines -- on which three flu strains would best protect the most people in the upcoming flu season. (Reporting by Maggie Fox; Editing by Will Dunham)
Copyright 2008 Reuters News Service. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
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