You know the rabies vaccine is one of the most dangerous vaccines you can give your dog. But unfortunately, if you live in the United States or parts of Canada, the rabies vaccine is required by law.

Maybe you try to mitigate the potential by asking for a thimerosal-free vaccine because you know that thimerosal is about half mercury by weight … and mercury is really (like really) bad for your dog.

If this sounds like you, then you really need to read on because you might not be getting what you paid for …

Why You Should Say No To Thimerosal

Thimerosal is a mercury-based vaccine additive that’s been used as a preservative for decades. Way back in 1935, five years after thimerosal was first added to vaccines, Eli Lilly (the creator of thimerosal), declared that thimerosal was completely safe. But the vaccine manufacturer Pittman-Moore wrote to them and said:

We have obtained marked local reaction in about 50% of the dogs injected with serum containing dilutions of Merthiolate (Thimerosal). Merthioiate is unsatisfactory as a preservative for serum intended for use on dogs.” (Director of Biological Services, Pittman-Moore Company, letter to Dr. Jamieson of Eli Lilly Company dated 1935. U.S. Congressional Record, May 21, 2003, E1018, page 9).

Since then, over 160 studies have also shown the dangers of thimerosal.

Thimerosal: A Sordid History

Since its introduction 80 years ago, thimerosal has suffered a less than spectacular track record:

  • In 1967, a study in Applied Microbiology found thimerosal killed mice when added to vaccines.
  • In 1972, Eli Lilly found thimerosal to be “toxic to tissue cells” in concentrations as low as one part per million (PPM), 100 times weaker than the in a typical vaccine.
  • Despite all of this ongoing and emerging data, Eli Lilly continued to promote thimerosal as nontoxic, even including thimerosal in topical disinfectants.
  • In 1977, ten babies at a Toronto hospital died when an antiseptic preserved with thimerosal was dabbed on their umbilical cords.
  • In 1982, the FDA proposed a ban on over-the-counter products containing thimerosal.
  • In 1991, the FDA considered banning Thimerosal from animal vaccines.
  • In 2006, researchers at UC Davis published a study connecting thimerosal with disruptions in antigen-presenting cells known as dendritic cells obtained from mice. Researchers and parents had previously proposed links between childhood vaccines and autism, a neurodevelopmental disorder that affects language skills and social interactions. The UC Davis study showed that in addition to being a direct neurotoxicant, thimerosal may also be an immunotoxicant, leaving the immune system vulnerable to microbes and other external influences.

Related: Want to learn more about vaccines and their ingredients? Click here and find out what your vet won’t tell you.

More Cover-Up

Despite all of the research to the contrary, the Center for Disease Control (CDC) assures consumers that “low doses of thimerosal in vaccines do not cause harm, and are only associated with minor local injection site reactions like redness and swelling at the injection site.” But authors Brian Hooker PhD et al recently took the CDC to task on this statement and they found that the CDC’s safety research is flawed and falsified.

The article, published in BioMed Research International, states that while there are over 165 studies that have focused on thimerosal, the CDC stance that there is “no relationship between [T]himerosal[-]containing vaccines and autism rates in children”  is based on just six studies, which were coauthored and sponsored by the CDC. Moreover, one of the studies cited by the CDC shows a 7.6 fold increased risk of autism in infants exposed to thimerosal.

Then in 2014, Hooker et al blew the lid off the CDC’s claims of safety and exposed their sponsored studies as biased, with some of these studies even showing thimerosal to decrease the risk of autism! Of course, the more than 150 independent studies found thimerosal to increase the risk of serious neurological disorders.

Why does this matter? Because your dog’s rabies vaccine contains this dangerous mercury-derived chemical. But what about the thimerosal-free vaccines? Is there really such a thing?

Thimerosal-Free Vaccines?

Today, veterinary vaccines still contain thimerosal – despite the dire warning signs that have been present for nearly a century. But what of thimerosal-free vaccines?

A few companies are making thimerosal-free canine rabies vaccines. Merial makes a thimerosol-free rabies vaccine called IMRAB 3 TF (the 3 designates a 3-year vaccine, and TF stands for “Thimersol-free”). There is also a 1 year version, IMRAB 1 TF. Fort Dodge makes a thimerosol-free rabies vaccine called RABVAC 3 TF. And more thimerosal-free vaccines may appear in the future.

That’s good news, right?

Well, not exactly. It seems that there’s a little-known vaccine ingredient called an excipient. These substances are used in the production of vaccines, but aren’t an actual ingredient that’s directly added to the vaccine.

Know where this is going?

That’s right – your thimerosal-free vaccine probably still has thimerosal in it. But because it wasn’t added directly to the vaccine, but used in production, the vaccine manufacturers can claim the vaccine is thimerosal-free!

And this isn’t just true for veterinary vaccines. According to the CDC, there are more than a few human vaccines marketed as mercury-free that actually have thimerosal in them.

So how do you know if the vaccine your vet wants to give your dog has mercury in it?

You can ask for the manufacturer’s data sheet for the vaccine and phone the manufacturer and ask them to email you a list of all of the vaccine excipients before you allow your vet to give that vaccine.

But is that enough? Will you get the truth?

Don’t count on it. Manufacturers can claim “proprietary confidentiality” when it comes to vaccine ingredients and even the FDA may not know what’s in them. Thimerosal-free vaccines may certainly be a better option than their mercury-containing counterparts … but the sad truth is we can only guess whether vaccines contain thimerosal or not. Even the thimerosal-free vaccines. . Consumers, and even the FDA, have no way of knowing if that vaccine truly is free of this dangerous neurotoxin.