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SLATE: Your Health This Month - the latest on bird-flu vaccine

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  • SLATE: Your Health This Month - the latest on bird-flu vaccine

    Your Health This Month
    Antibiotics and asthma, Caesarean sections, the latest on bird-flu vaccine, and more.
    By Sydney Spiesel
    Posted Tuesday, April 4, 2006, at 1:21 PM ET

    This month, Dr. Sydney Spiesel discusses where there's a link between antibiotics and the development of asthma, why the rate of Caesarean deliveries is rising, the latest on bird-flu vaccine, and the importance of malaria medications.


    Bird-flu vaccine: Can we make enough of it in time?

    The fear: We wait in America, holding our breath, to see if H5N1 influenza will come to our shores. It will. We also hold our breath, along with the rest of the world, to see if this flu that's so lethal and contagious for birds will change and become similarly lethal and contagious for humans. At least once before, in 1918, a bird flu mutated and killed between 50 million and 100 million people worldwide. What's the latest on trying to prevent another pandemic?

    Quarantine: Traditionally, three methods have been used to control epidemics. By imposing quarantine, a society can force physical containment of infectious people. Historically, this has rarely worked. Because influenza is so infectious, it would be hard to control an epidemic even if only a few people slip out of quarantine (or turn out to be infectious before the nature of their illness becomes clear).

    Treatment: For flu, the treatment choices are not so good and are getting worse. There are presently two classes of medication. One, amantadine, has become completely worthless for H5N1 flu because the virus is now uniformly resistant to it. The second, Tamiflu, is effective for now. But there is evidence that if the drug were to be widely distributed (as it would be in an epidemic), the virus would likely become resistant to it, too.

    Immunization: That leaves vaccines. This method is especially attractive because we have experience with using vaccines to prevent influenza and because immunization is an inherently efficient method of warding off illness. Vaccines transform patients into their own medicine manufacturers by priming them to produce protective antibodies?effective, specific medications, made by the body and generally delivered exactly to the site where they are most needed.

    State of the science: So, can we depend on flu vaccines to protect against H5N1 flu? That is the question addressed in a recent report by a team headed by Dr. John J. Treanor of the University of Rochester. Conventional flu vaccines?the kind many of us take annually?are made from influenza virus grown in fertile chicken eggs, starting with the strain of human influenza predicted to be important for each anticipated flu season. For Treanor's study, an influenza vaccine was made using the same technology, with starting material collected during an outbreak of H5N1 in Vietnam. A wide range of doses were given to a group of human subjects to determine 1) whether the vaccine was safe and 2) how much of the vaccine's active ingredient was required to generate production.

    Results: Here's the good news: In the right dose range, the experimental vaccine more than half the time stimulated the development of what we assume are protective antibody levels. Side effects were common but generally minor (for instance, local pain and tenderness at the injection site). But here's the bad news: It took about 12 times as much of the experimental vaccine as is usually in an annual flu shot to provide a roughly comparable level of protection. Well, that wouldn't be so bad?except that factories now working at absolutely full capacity can't keep up simply with the current need. If you were one of the many people who couldn't get a flu shot this year, I don't need to point out that even in a relatively mild flu season, demand exceeded supply.

    Conclusion: So, we now have a promising but weak H5N1 vaccine. We need to find ways to manufacture it in much larger quantities than are presently possible (click here and here for two proposals) or to dramatically increase its potency. And the clock is ticking.