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    Vaccine FAQ

    Vaccine Benefits, Vaccine Risks: 10 Basic Questions Answered

    4. If only to err on the side of caution, why can't all vaccines be thimerosal-free? continued...

    "To get thimerosal out of all vaccines would require additional construction of facilities to be able to prepare vaccines differently. So there have been major changes since 1999 in removing thimerosal from the vaccine supply, but it is a many-year process. Although there is no compelling evidence that thimerosal caused harm, the concerns that have been raised have led to this lengthy process.

    "Some of the pharmaceutical companies are going through the transition. Not looking for another preservative, but looking for production capacity to make that change.

    "But right now, for every childhood vaccine, there is a thimerosal-free alternative."

    5. Can vaccines cause the diseases they are supposed to prevent? Every year you hear people say, "I got my flu shot and then I came down with the flu."

    "Flu vaccine does not cause the flu," says Schuchat. "Many vaccines do not provide 100% protection, but they decrease the chances of getting an infection. Even so, they don't reduce the chances to zero. Sometimes, even a person who is vaccinated can get an infection the vaccine was supposed to prevent. But the vaccines used today don't cause the diseases they are supposed to prevent."

    6. What harms do vaccines do?

    "There can be side effects from each individual vaccine," says Schuchat. "The most common side effect is pain or swelling at the site of injection. For each vaccine recommended, the CDC is required to provide a vaccine information statement to a parent or patient receiving one of the vaccines. It lists background information on benefits and risks. Most vaccines do not have serious adverse events associated with them.

    "But some do. For instance, the flu vaccine is made from eggs. People with egg allergies should not receive the flu vaccine because they can have a serious reaction. So there are questions doctors use to screen people before getting any vaccine to make sure they don't have special risks. For the vast majority of childhood vaccines, there are very few of these.

    "There is a possibility -- it is not yet clear -- but with the meningococcal conjugate vaccine, there have been reports of Guillain-Barre syndrome. We do not yet know if this is a true vaccine-related risk. But if it is there, it happens at the rate of about one per million doses administered. And that has been added to the vaccine information sheet."

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