It can be argued that vaccines are one of the greatest developments of the 20th century; millions of lives are saved annually and several infectious diseases have been eliminated or eradicated completely. While there are no federal laws mandating vaccinations, all 50 states require them for children attending public schools, although they all allow for exemptions based on religious or philosophical reasons.

Critics argue that the government shouldn’t have the final say in what we do to our own bodies, however, while others contend that many of the questionable ingredients in vaccines can lead to scary side effects.

To complicate matters, there’s a ton of misinformation swirling around on the Internet: the all-powerful reach of big pharma has some questioning whether the data can be trusted, while many of the more vocal anti-vaccine voices have been dismissed as quacks. No matter what side of the aisle they ultimately land on, I want my patients to have all the facts so that they can make the most informed decision.

This series of articles will address the ingredients found in many of the 9 distinct vaccines the Center of Disease Control (CDC) recommends children have by the time they are six. These 9 vaccines are administered in 29 visits, and annual flu shots (also recommended by the CDC) make for additional exposure to these substances.

A preservative known as thimerosal is used to kill pathogens in vials containing multiple doses of a vaccine. Thimerosal is approximately 50% mercury by weight and a typical vaccine might contain 0.01% thimerosal, or 25 micrograms of mercury per 0.5 mL dose. For comparison, this is roughly the same amount of elemental mercury contained in a 3-ounce can of tuna fish. (1)

Mercury is known to be harmful to humans, and its effects vary depending on the form and level of exposure. Acute exposure to mercury vapor can adversely affect the nervous system, causing psychotic reactions, delirium, hallucinations, and suicidal tendencies.

Continued exposure can produce violent muscular spasms and even death. In 1999, the FDA was required to assess the amounts of mercury in vaccines and reported that the amount of thimerosal they contained was a safe quantity. In fact, they went so far as to say that there was no evidence that it is even dangerous (2).

The biggest argument in defense of thimerosal is that it is an ethyl mercury, which is different from the type of mercury we are most familiar with, methyl mercury—the kind that naturally accumulates in fish. It is this difference, the ethyl versus methyl, that lead the World Health Organization (WHO) to publish a report stating that the amount of mercury in vaccines is safe.

Apparently ethyl mercury has a shorter half-life in the body (less than one week) than methyl mercury (1.5 months) and is excreted through the gut, unlike methyl mercury, which prevents a build up in our systems. The apparent conclusion of the WHO is that the mercury we consume through seafood sources is much more toxic than the very tiny amount of ethyl mercury used in some vaccines.

But does that really make it okay? Both ethyl- and methyl mercury are organic compounds of mercury, which happen to be the most toxic to humans. A report (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC30960...) from the US National Library of Medicine states that acute or chronic mercury exposure can cause adverse effects during any period of development. It states that “because mercury is a highly toxic element, there is no known ‘safe’ level of exposure.

Ideally, neither children nor adults should have any mercury in their bodies because it provides no physiological benefit.” Let that sink in. No amount is known to be safe. And yet the FDA and the WHO say that the small amounts in vaccines are?

What about those small amounts in conjunction with the mercury we’re exposed to through environmental and dietary sources. Are tiny amounts still okay when they’re piled on top of everything else?

The report also stated that fetuses and infants are especially vulnerable to mercury exposures, and that neurological damage caused by mercury exposure is very likely to be permanent. Given that pregnant women and young children are precisely who the majority of vaccines are intended for, this news is unsettling, to say the least.

To add to the confusion, Robert F. Kennedy Jr. published a report in 2005 that suggested a correlation between thimerosal and autism. The medical community responded that his claims were unsubstantiated, and Kennedy was dismissed as a fear-mongerer.

Because of the attention Kennedy’s report caused however, the decision was made to reformulate vaccines to remove it. Not before using up all the old formulations of vaccines however; they were just shipped overseas for use in third-world countries.

Today the majority of vaccines are formulated without thimerosal, with the exception of flu shots. What most people don’t realize, however, is that a formulation always exists that does not contain the questionable ingredient.

No matter what stance you take on this matter, make certain you request thimerosal-free shots for yourself and your families. Stay tuned for the next installment in this series: everything you ever wanted to know about aluminum.