It’s natural for parents to want to ensure that their children are getting food and medications that are healthy and wholesome, free of dangerous contaminants.
It’s a rare parent who hasn’t heard that eating certain kinds of fish, or eating large quantities of some other kinds of foods, isn’t healthy for young children because of the amounts of methylmercury that have accumulated in them.
No wonder parents reacted with alarm more than 15 years ago when they learned that another form of mercury was used as a preservative in routine childhood vaccines. But when it comes to vaccine ingredients, there’s a very big difference when you get to the details. Thimerosal, the preservative that used to be common in vaccines, contained ethyl mercury, not methylmercury. They rhyme perfectly, but beyond that, there’s a significant difference—largely that ethyl mercury stays in the body for a much shorter time, and doesn’t bioaccumulate, or build up, in tissues.
Some vaccine ingredients list might seem scary at a glance, but when you dig into the science, research shows them to be very safe. Here are some examples:
In our bodies, thimerosal breaks down into ethyl mercury and thiosalicytate, both of which are readily eliminated from the body, according to the U.S. Centers for Disease Control and Prevention. That’s not true of methylmercury, the neurotoxin that occurs in the aquatic environment and as a result is found in fish. Unlike ethyl mercury, methylmercury builds up over time in the fish; the amounts tend to be highest in top-of-the-food-chain fish that eat other fish.
One 2011 study looked at adults who were undergoing treatment with a thimerosal-containing vaccine used for chronic fatigue syndrome. Within a few weeks of repeated injections with that vaccine, the levels of ethyl mercury in their blood were back down to normal. In fact, the researchers found, their blood levels of methylmercury from eating fish were much higher than their ethyl mercury levels.
There has never been any evidence that thimerosal harmed children or anyone else who received vaccines. But because of the public concerns and as a precaution, manufacturers began producing thimerosal-free vaccines about 15 years ago.
It’s interesting to note that a small number of people have expressed concern that thimerosal may cause autism. Many large-scale studies have shown that vaccines are not linked to autism. But in addition, much of the concern about vaccines and autism has revolved around the MMR vaccine—for measles, mumps and rubella—after a fraudulent, retracted study by Andrew Wakefield. Yet the MMR vaccine has never contained any thimerosal.
There’s no doubt that in large quantities, formaldehyde — in large enough doses — can be a dangerous substance that damage DNA and causes cancerous changes in cells. But when parents worry about formaldehyde in vaccines, they probably aren’t aware that, in small quantities, formaldehyde is also naturally present in our bodies—and in fact, serves an important purpose for our health.
“Formaldehyde is essential in human metabolism and is required for the synthesis of DNA and amino acids (the building blocks of protein),” according to Children’s Hospital of Philadelphia. “Therefore, all humans have detectable quantities of natural formaldehyde in their circulation.”
In vaccines, formaldehyde is used to inactivate viruses so that they don’t cause disease, and to detoxify bacterial toxins, including the one used in the diphtheria vaccine, according to the FDA.
The amount of formaldehyde found in an average 2-month-old baby is about 1.1 mg., at least five times as much as the baby would be exposed to in vaccines, Children’s Hospital of Philadelphia reports. Vaccines have less than 1% of the formaldehyde found in an average-sized pear.
By the time the vaccine is given, only trace amounts remain.
Aluminum salts are used in some vaccines as adjuvants—substances that enhance the recipient’s immune response. Aluminum has been used in vaccines for about 70 years, according to the CDC, and babies get much more of it from food than from vaccines.
“The aluminum contained in vaccines is similar to that found in a liter … of infant formula,” Children’s Hospital of Philadelphia reports. “While infants receive about 4.4 milligrams of aluminum in the first six months of life from vaccines, they receive more than that in their diet.”
Rumors have been spread that some vaccines contain antifreeze. This simply is untrue and according to the CDC, it never has been true.
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