Thimerosal is used as a preservative, and is only a tiny portion of the vaccine. Each dose has about 25 micrograms of mercury in it. That's 0.025 milligrams, or 0.000025 grams. And if you like fish, you've probably eaten much more mercury this year than you'll get from a vaccine. Oh, and it's also in all the vegetables we eat – even organic ones.
Vaccines given to children and pregnant women do not contain thimerosal as a preservative and so only contain trace level of mercury, if any.
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