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H1N1 Swine Flu Vaccine FAQ

WebMD provides a practical guide to the H1N1 swine flu vaccine.

What's the difference between the nasal spray and injectable vaccines? continued...

The advantage of the nasal spray is that in children who have never had the flu or a flu vaccine before, it seems to elicit a stronger immune response than the flu shot.

The disadvantage of the nasal spray is that in older people who've had the flu or flu vaccines before, it may not be quite as protective as the flu shot. That finding is based on a single study, based on just a single flu season. And since nobody has had the H1N1 swine flu before, the FluMist H1N1 swine flu vaccine is expected to work just as well in adults as the flu shot does.

I know studies show vaccines preserved with thimerosal are safe, but is there an alternative?

Tin Tiny doses of a mercury compound called thimerosal keep multidose vials of flu vaccine safe from contamination with bacteria. Before thimerosal was added to multidose vials, contamination caused serious adverse events.

Exhaustive studies fail to find any reason to believe that thimerosal is unsafe. But if you don't want thimerosal, you don't have to have it. Single-dose syringes of flu vaccine don't need thimerosal and don't have any. Neither does the FluMist nasal spray vaccine.

If you prefer a thimerosal-free vaccine, check with your provider to see if one is available. If not, check with your state or local health department to see where you can find one.

I've heard that something called squalene is in the vaccine. Is that true?

None None of the U.S. H1N1 swine flu or seasonal flu vaccines contains squalene.

Squalene isn't a very nice sounding word, but it's an oil that's a natural part of many body processes. It's widely used in cosmetics because it penetrates the skin easily without leaving an oily feel.

Squalene is also used in substances called adjuvants. When mixed with vaccines, adjuvants make vaccines work better at lower doses.

The U.S. purchased millions of doses of these adjuvants in case the H1N1 swine flu vaccine had to be boosted to be effective. That turned out not to be necessary. Unlike current H1N1 swine flu vaccines, a vaccine with adjuvant would have to be specifically approved by the FDA. Such vaccines could be used this year only under the FDA's Emergency Use Authorization. No such authorization has been issued.

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