The Safety of Vaccine Ingredients: Part Two (Mercury)

In our last blog post, we looked at aluminum in vaccines, why it’s included, and what makes it safe.

Today we’re turning our attention to mercury, one of the most easily misunderstood vaccine ingredients.

Mercury in vaccines

When you hear about mercury, you’re likely hearing about the form that’s found in fish and pollution.

That form is called methyl mercury, and it can be harmful if accumulated in the body. Methyl mercury, however, is not in vaccines.

There’s another form of mercury called ethyl mercury, which can be more easily processed by the body and doesn’t accumulate. Ethyl mercury is a component of an ingredient called thimerosal, which used to be in vaccines.

As a safe form of mercury, thimerosal used to serve as a preservative in vaccines.

Even though thimerosal is not harmful, its association with mercury in general caused a lot of confusion and unease, so it was removed from childhood vaccines in 2001 to ease parents’ concerns.

Now, childhood vaccines do not contain thimerosal, or any other form of mercury.

Some formulations of the flu vaccine contain trace amounts mercury, but the body processes it out quickly. And even though thimerosal has been removed from all other vaccines recommended for children, there’s still a lot of misinformation swirling in the public about its effects on the body. Pseudoscientific sources have tried to link thimerosal with autism, but studies continue to find no association with autism or other health problems. (Source: “Vaccine Ingredients: What You Should Know”)

Stay informed

The next time someone mentions their concerns about mercury in vaccines, help clear up the confusion and let them know that mercury is no longer contained in childhood vaccines.

If you have any other questions about vaccine ingredients, visit or talk to your pediatrician.

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