Thimerosal free dog rabies vaccines have been recently introduced as a result of concerns over unhealthy ingredients found in the rabies vaccine for dogs. Among vaccines for humans, thimerosal has been used for quite some time, and is still routinely added to certain types of flu shots, but there have been growing concerns about its use. While to a large extent the use of flu vaccines containing thimerosal has been largely decreased over the past 10 years in the United States, in the veterinary field, things are slowly progressing with the development of thimerosal free dog rabies vaccines.
Thimerosal in Vaccines
According to the Centers for Disease Control, thimerosal is a preservative that is ethyl-mercury based. Why do vaccines need preservatives?
Preservatives are needed so to prevent contamination of the vaccine with germs, bacteria and fungi in multi-dose vials. Multi-dose vials are vials that contain more than one dose and are labeled to be used for more than one patient; however, special aseptic techniques (meant to be free from contamination) need to be followed.
Every time a syringe needle enters a vial, when a vaccine is about to be administered, there are risks for contamination which can potentially cause severe local reactions, illness and even death. The addition of thimerosal has been used since the 1930s to help prevent such contamination.
According to CDC, thimerosal doesn't remain in the body for long because it breaks down into ethylmercury (not to be confused with methylmercury, the mercury found in fish) and thiosalicylate which are readily eliminated from the body. Its use as a preservative for vaccines is therefore considered safe and this is backed up by peer-reviewed scientific studies which support its safety. However, some minor side effects may occur such as redness and swelling at the injection site. In some rare cases, allergies are a possibility.
Thimerosal has been suspected to cause autism in children, but yet, despite the fact that thimerosal has been removed from vaccines for children since 2001, the number of children diagnosed with autism continues to rise. A study was also able to disprove the possible link between vaccines and autism.
Decreased use of thimerosal in vaccines is in part due to the development of new vaccines offered in single-dose vials. However, according to the Food and Drug Administration, thimerosal was specifically removed from children's vaccines in an attempt to reduce an infant’s total exposure to mercury, considering that nowadays exposure to several environmental sources of mercury may be difficult to eliminate.
Nowadays, vaccines developed for children are available in formulations that are thimerosal-free and many vaccines for adults are also nowadays offered in a thimerosal-free option. Certain flu vaccines though may still contain thimerosal.
Thimerosal in Dog Rabies Vaccine
The veterinary field is often keeping up with the many changes taking place in the medical field. It is expected therefore that pet vaccines should also reflect the changes occurring in the medical field for humans.
There are not many studies conducted on dogs, but some studies are interesting. One study in particular, looked for traces of mercury in dog hairs. As in the case of dogs consuming fish, it was expected to find traces of mercury from dogs vaccinated with vaccines containing thimerosal.
The results demonstrated that thimerosal did not increase the content of total mercury in dog's hairs. However, results showed that fish consumption from ingesting fish granules, fish treats and fresh fish did. This seems to suggest that feeding fish is more concerning than giving dogs vaccines with thimerosal!
Yet, the use of thimerosal is subject of debate. While on one hand there are studies that seem to prove its safety, on the other hand, there are others that do not support this view. A very thorough read with references to countless studies conducted over the years comes from the Journal of Toxicology and Environmental Health, January 2008. The literature can be found on the Research Gate website.
The literature concludes that "The high order of toxicity from Thimerosal and its ethylmercury breakdown product has been known and published for decades. Nonetheless, Thimerosal remains in the drug supply, especially in various vaccines manufactured both for the United States and globally."
"Thimerosal is a weak antibacterial agent that is rapidly broken down to products, including ethylmercury residues, which are neurotoxic. Its role as a preservative in vaccines has been questioned, and the pharmaceutical industry considers its use as historical."~Seal et al. (1991)
Thimerosal Free Dog Rabies Vaccines
IMRAB TF is a thimerosal free dog rabies vaccine produced by Merial. The TF is simply the abbreviation for thimerosal-free. It was possible to develop this vaccine free of the thimerosal preservative because it comes in an individual dose package versus multi-dose vials.
IMRAB TF comes into two different forms: IMRAB TF-1 and TF-3. In this case the 1 and the 3 are meant to depict their validity. IMRAB TF-1 is the one-years rabies vaccination while IMRAB TF-3 is the 3-year rabies vaccination.
Finding a vet's office that stocks thimerosal free dog rabies vaccines can be at times challenging. It may be worth calling around several vet offices though.
If vets do not have thimerosal-free dog rabies vaccines in stock, ordering it may be an option, but the problem is that in order to order this specific type of vaccine, vets must often purchase a whole lot of 50 vials which can turn out being costly.
""Merial is responding to the needs of veterinary professionals looking for alternatives to vaccine additives." ~ Dr. Zack Mills, executive director of Veterinary Services for Merial.
- Ball LK, Ball R, Pratt RD. An assessment of thimerosal use in childhood vaccines. Pediatrics 2001;1147-1154
- Hviid A, Stellfeld M, Wohlfahrt J, Melbye M. Association between thimerosal-containing vaccine and autism. JAMA. 2003;290:1763–6.
- Global Vaccination Recommendations and Thimerosal, Walter A. Orenstein, Jerome A. Paulson, Michael T. Brady, Louis Z. Cooper, Katherine Seib, Pediatrics, January 2013, VOLUME 131 / ISSUE 1
Neuro Endocrinol Lett. 2013;34 Suppl 2:90-4.Total mercury content in canine hair before and after administration of vaccines containing thiomersal. Sedlackova L1, Kral T2, Sevcikova M2, Kruzikova K2, Svobodova Z2.
- Seal, D., Ficker, L., Wright, P., and Andrews, V. 1991. The case against Thiomersal. Lancet 338:315–316
- A Review of Thimerosal (Merthiolate) and its Ethylmercury Breakdown Product: Specific Historical Considerations Regarding Safety and Effectiveness,Journal of Toxicology and Environmental Health Part B 10(8):575-96 · January 2008
- Merial News Release, States Give Green Light to Merial's One-Year, Thimersol-Free Rabies Vaccine