Why Does the FDA Warn About Mercury in Fish, but Not Mercury in Flu Shots?

The FDA and EPA began to warn certain high risk groups about eating fish that might be contaminated with high levels of mercury in 2004.

Although it was known that “nearly all fish and shellfish contain traces of mercury,” this wasn’t thought to be a health concern for most people. Higher levels of mercury in certain fish could be though, especially for young children, nursing mothers, pregnant women, and women who might become pregnant.

That’s why the EPA and FDA recommended that those high risk groups not eat Shark, Swordfish, King Mackerel, or Tilefish (have highest levels of mercury) and limit eating other fish that are lower in mercury.

Why Does the FDA Warn About Mercury in Fish, but Not Mercury in Flu Shots?

So why do experts warn about mercury in fish, but don’t warn about mercury in vaccines?

Trace Amounts on “Ten Lies” Told About Mercury in Vaccines
Trace Amounts thinks that they have uncovered “Ten Lies” about mercury in vaccines

While that is a good question, the most obvious answer is that there are a very limited number of vaccines that you can get that contain any mercury (thimerosal), while if there was no warning, you could theoretically eat a ton of fish that are contaminated with at least some mercury.

And since 2001, thimerosal-free versions of non-flu vaccines have been available. There has also been an increasingly large supply of thimerosal-free flu vaccines available since 2003.

So how much mercury from vaccines could pregnant women and young children really be getting?

Remember, the only routine vaccines that pregnant women get are Tdap (never contained thimerosal) and the flu vaccine. And all of the routine vaccines young children receive are now thimerosal-free, including DTaP, Hib, IPV, Rotavirus, and Prevnar. All children should also get a flu vaccine once they are six months old, but like the flu vaccines for pregnant women, thimerosal-free flu vaccines are available.

Still, if they didn’t get a thimerosal-free flu shot, it would mean that they got the amount of mercury from one flu shot each year, or 25mcg. Some children could get up to 50mcg if it was their first season getting a flu vaccine, as they might need two doses of the flu vaccine.

The FDA and EPA offer very specific recommendations on how much fish to eat to avoid mercury.
The FDA and EPA offer very specific recommendations on how much fish to eat to avoid mercury.

How much mercury do you ingest when you eat fish? It depends on the fish, which is why the recommendations on which fish to eat and avoid are so specific. In general, it can range from 4mcg for salmon, 60mcg for canned albacore tuna and 170 mcg for swordfish.

While you are supposed to avoid the fish with the highest mercury levels, you might be eating the other fish each week, so unless you don’t like to eat fish, it is almost certainly going to quickly add up to much more than you get from your yearly flu vaccine, which you likely avoided anyway by getting a thimerosal-free flu shot.

And with fish, the mercury is in the form of methymercury, 95% of which is absorbed into your bloodstream. In contrast, thimerosal in vaccines breaks down to ethylmercury and is eliminated from your body quicker than methylmercury.

But if fish contains mercury, why not just tell people to avoid eating fish?

“Most fish are an excellent source of high quality protein. Fish are also important sources of selenium, zinc, iodine, iron, and other minerals needed by the body. Fish are natural sources of many B vitamins, and oily fish provide vitamins A and D. Studies with pregnant women have found that the nutritional benefits of fish, like other protein-rich foods, are important for their children’s growth and development during pregnancy and childhood. Most fish are low in fat, and most of the fat that is present in fish is healthy polyunsaturated fat. The polyunsaturated omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are also present in many types of fish. Research is still underway to determine the health benefits of omega-3 fatty acids.”

Questions & Answers from the FDA/EPA Advice on What Pregnant Women and Parents Should Know about Eating Fish

Fish have a lot of important nutrients, so are good to eat. So you balance the benefits of eating fish with the risks of mercury contamination and we get the sensible advice to limit the amount of fish you eat.

When you do the same kind of analysis of the risks and benefits of vaccines, even those with thimerosal, the benefits are still greatly in favor of getting vaccinated to prevent life-threatening infections. Remember, thimerosal was removed from vaccines as a precautionary measure and not because it was proven to be dangerous. In fact, many studies have shown that thimerosal in vaccines is not harmful.

What to Know About Mercury in Fish and Vaccines

Comparing mercury in fish and vaccines is like comparing conventionally grown apples and pears, at least it would be if someone figured out how to make an edible vaccine in the form of a pear.

More on Mercury in Fish and Vaccines

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