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Flu shot in the dark misses target

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  • Flu shot in the dark misses target

    Flu shot in the dark misses target
    UPDATED: 2008-04-18 02:41:41 MST


    TORONTO -- A study finds this year's flu shot gave modest protection against influenza A strains in North America and no protection against the influenza B strain Canadians were most likely to encounter.

    The U.S. Centers for Disease Control says overall, the vaccine was about 44% effective this flu season. Experts generally estimate flu shots are up to 90% effective in protecting healthy adults.

  • #2
    Re: Flu shot in the dark misses target

    A Jump in Doctor Visits and Deaths in Flu Season

    Published: April 18, 2008

    The current flu season has been more severe than the last three, with more doctor visits and more deaths from flu and pneumonia, federal health officials are reporting.

    The season peaked in February, when flulike illnesses accounted for 5.9 percent of doctor visits. Over all, doctor visits for these illnesses were higher than normal for 13 consecutive weeks.

    The death rate related to flu and pneumonia was also higher than usual for 13 consecutive weeks; at the worst point, in March, the illnesses were listed as underlying or contributing causes of death in 9.1 percent of deaths. Any rate over 6.9 percent is considered unusually high.

    The deaths included 65 children under 18. The youngest was a month old, and the median age was 4.5 years. In each of the three previous flu seasons, 46 to 74 children died.

    The statistics were published online on Thursday by the Centers for Disease Control and Prevention.

    The main reason for the increased severity this season is that a more virulent type of virus, called A(H3N2), has predominated, said Dr. Dan Jernigan, deputy director of the influenza division at the disease centers. There are many A(H3N2) variants, and this particular one was first identified in Brisbane, Australia, in 2007.

    The virus caught vaccine makers off guard. Though the current vaccine does contain an A(H3N2) strain related to the Brisbane variant, it is not exactly the same, making the vaccine less effective than it might have been.

    A study found that the vaccine reduced people?s risk of contracting any type of influenza A by 58 percent. But when vaccine strains are well matched to viruses, they can cut the risk by 70 percent to 90 percent in healthy adults. Generally, the vaccines do not work as well in the elderly or in small children.

    Normally, if 100 people who are not vaccinated are exposed to the flu, 10 will get sick. But if 100 who are vaccinated are exposed, and the vaccine is 70 percent effective, then only 3 will get sick.

    Flu vaccines generally contain three types of virus, and this year?s vaccine has a second mismatch as well: it is completely inactive against the kind of influenza B virus that has been circulating this year.

    Dr. Jernigan said mismatches could occur because vaccine makers must decide which strains to include by February, many months before the flu season begins, so that they can make the vaccine in time for autumn. Sometimes, he said, ?a virus will emerge that was not even available at the time the decision had to be made.?

    The vaccine for the next flu season has been formulated; it will contain three completely different strains from the ones used this year.

    Articles published Thursday in two scientific journals, Science and Nature, discussed the evolution and spread of influenza A viruses. Researchers have long believed that new flu viruses originated each year in Asia, and the Science article provided evidence that the theory was correct. Its authors analyzed 13,000 flu virus samples from around the world and traced them to East and Southeast Asia.

    Many scientists had believed southern China was the main source of flu viruses, but the new study suggests they come from other parts of Asia as well. The viruses reach Europe and North America six to nine months later and then after a few more months arrive in South America, where they die out.

    The disease centers estimates that every year 5 percent to 20 percent of the United States population gets the flu, and that more than 200,000 people are hospitalized because of flu complications and about 36,000 die.


    • #3
      Re: Flu shot in the dark misses target

      Flu season hit the rest of the nation harder than Seattle
      It was among the worst in some areas


      Last updated April 17, 2008 9:34 p.m. PT

      Federal health officials say the nation is winding down one of its worst years for influenza, thanks in part to a poorly matched vaccine, but residents of Seattle and King County appear to have suffered through only a typical flu season.

      "Flu is still around, but it's definitely on the decline," said Matias Valenzuela, a spokesman for Public Health -- Seattle & King County. "It's been a pretty routine year here as compared to other parts of the country."

      The Centers for Disease Control and Prevention on Thursday issued its regular weekly report highlighting nationwide flu statistics. Among the federal agency's findings was an acknowledgement that the vaccine prepared in anticipation of this year's flu season was very poorly matched to the dominant strains of the virus.

      "We had a less than optimal match," said Dr. Dan Jernigan, a flu expert with the Atlanta-based CDC. Based on a sampling done in Wisconsin, public health officials said people who received this year's flu vaccine were only 44 percent less likely to get the flu as compared with the typical 70 percent protection from seasonal immunization.

      Because the flu virus comes in a variety of strains and mutates rapidly, it is always a bit of a guessing game for officials to decide which of three strains to include in the vaccine. The flu vaccine continues to be made by growing the virus in chicken eggs, an old, cumbersome and time-consuming laboratory process.

      CDC officials also reported that some cases of flu were resistant to Tamiflu, an anti-viral drug that King County officials and other government agencies have spent millions of dollars on to stockpile in the case of a flu pandemic. Flu infects 5 percent to 20 percent of the U.S. population on any given year and kills an average of 36,000 people nationwide.

      Valenzuela said it's not clear why the Seattle and King County area has had a relatively typical flu season as compared with the rest of the country, especially since the vaccine also poorly matched with the predominant flu strains circulating in this region.

      "But there are always regional differences in the way flu plays out every year," he said. "One thing we can always say is that influenza season is unpredictable."

      ON THE WEB

      To learn more about flu season here,


      • #4
        Re: Flu shot in the dark misses target

        44% "effective" to reduce laboratory confirmed influenza only.
        No effectiveness was observed to reduce FLI.

        When you have flu-symptoms, it doesn't really matter to your health
        whether they can confirm influenza in the lab.
        So I'd say the flu-shots were useless this year.

        Hopefully in a pandemic, when the particular strain is targeted
        and vaccination coverage is bigger, then there will be "herd immunity" ...
        I'm interested in expert panflu damage estimates
        my current links: ILI-charts: