Mercury, in a cat rabies vaccine, is dangerous but is it in the vaccine?

We are told that pet owners and veterinarians should use mecury-free rabies vaccines. In fact that applies to any vaccines. This is because mercury is toxic to pets and people (as I understand it). It is used as a preservative and/or antiseptic in vaccines. I am also told by Drs Becker and Shultz that mercury is not in human vaccines:

“We know that thimerosal, an adjuvant included in human vaccines, has been removed due to health concerns…”

I am further informed by Dr. Ronald Schultz, a pioneer and expert in the field of veterinary vaccines, that he is not aware of any veterinary vaccine that contains “Thimerosal”. Thimerosal is one of the names for mercury additives to vaccines. Another two are: Thiomersal, Merthiolate

But……Dr. Cathy Alinovi DVM writing on the well-respected website Truth About says that there are four commonly administered rabies vaccines for dogs and cats and all but one (perhaps) contains mercury under one of the complicated names they give such as Merthiolate.

Okay. Confused? I am. The only one that is listed in Dr. Cathy Alinovi’s article which does not contain mercury appears to be: Boehinger Ingelheim’s Rabvac but even then I can’t be sure because it contains a “proprietary adjuvant”.

I need clarification. We know that mercury should not be in vaccines or at least that is the way I read the situation. But it is complicated. The trouble is this: which cat rabies vaccines don’t contain mercury?

I am further informed that all Merial vaccines are mercury-free according to this website.

Whatever…just make sure that you ask your vet to use mercury-free rabies vaccines. The rabies vaccine is mandatary in every state of America. That means a lot of cats being vaccinated. Let’s not harm them unnecessarily.

Note: this is a very complicated area of veterinary medicine. I am not a vet. I have deliberately kept things straightforward and focused on one topic to simplify the article. If there is an error in it please tell me and I will amend it promptly.


  1. What are the ingredients of vaccines?And
  2. The vaccine that is mandatary.

7 thoughts on “Mercury, in a cat rabies vaccine, is dangerous but is it in the vaccine?”

  1. Vet writes, with case examples, how pet owners need to do their research so pets get appropriate, safest vaccinations for their region and must avoid over vaccination. –

    I phoned Murial to speak with an area sales rep find a vet in a nearby city with their vaccine as none of the five or so clinics locally carry it.

    • Many thanks Chris. I totally agree that cat owners need to play their part in ensuring that cat vaccinations are as safe as possible. It is hard though for cat owners to question a veterinarian.

    • Many vets don’t carry Murial Purevax because of the cost. Seems that many of the same pet owners screaming about safe vaccinations balk at the few extra dollars to provide one.

  2. Real vets are following the current vaccine recommendations. Demand only adjuvant free vaccines. If the vet you are going to doesn’t offer them you should probably wonder what else they are aware of.

  3. The whole mercury thing is a made up scare by the anti-vaxxers. Some human vaccines have thimerosal preservative which is an organic compound methylmercury and is not the same as toxic ethylmercury. Unike Ethyl mercury, methylmercury is quickly eliminated from the body. It’s been present in human vaccines since 1930 and is perfectly safe. Now, some time ago, there was a fraudulent study that claimed to link thimerosal with autism. It was later found to be a fraud. But as a result, thimerosal was eliminated from children’s vaccine, and guess what – it didn’t make any difference in rates of autism. It’s still present in many adult vaccines.

    Thimerosal is a preservative i.e. it’s added to vaccines to store them longer.

    It’s not the same as an adjuvant present in some cat vaccines. An adjuvant is from aluminium and it’s purpose is to increase inflammation that would increase immunity. Adjuvants are suspected (but not proven) to be responsible for rare sarcomas in cats. It’s suspected that because adjuvanted vaccines result in greater inflammation that persists and that some cats are extremely sensitive to local inflammation, non-adjuvanted vaccines i.e. Merial Purevax vaccines are safer. They are also more expensive, and as most vets haven’t switched to 3-year version yet (which cost 3 times as much as one-year Purevax Rabies) needs to be administered every year.

    The current thinking re: Rabies cat vaccine is – it’s better to pick a vet that uses non-adjuvanted vaccines since while it can also cause sarcomas (any injection in cats can), there is no evidence it causes more sarcomas and some evidence that it might cause less. If you can get the vet that uses 3-year Purevax – great, if not, go for 1 year Purevax.

    • Thank you Kitty for adding your expertise to this page. I think that you would agree that vaccines are a complicated subject. As a layperson, I am getting conflicting information. I don’t know what is dangerous and what is not dangerous but I do know that mercury per se is dangerous to humans and therefore to cats. My article points to conflicting information from experts. I don’t think that helps the average cat caretaker understand what is best for their cat in respect of vaccinations.

      I am not sure that I can agree with you that this is scaremongering by people who are against vaccinations. We know that vaccinations have improved over the years but vaccinations are not an automatic benefit to cats. There are some downsides and some dangers and vaccinations are really about risk-how to minimise the risk of disease and ill-health but they do present a risk in themselves to domestic cats. It’s about balancing those risks.

      • Every medical intervention has benefits and risks; however, before we get to it, let me give you an example regarding methyl mercury vs ethyl mercury. Both ethyl mercury and methyl mercury are compounds of mercury, but while ethyl mercury is an industrial pollutant, methyl mercury is preservative that kills bacteria, and while it may be toxic if consumed in large doses, it’s perfectly safe in small doses. It also has a short half life and is eliminated from the body quickly. The difference between ethyl mercury and methyl mercury is comparable to the difference between ethyl alcohol (ethanol) and methyl alcohol. Ethyl alcohol is present in antifreeze and drinking a few shots would kill you. Methyl alcohol is your regular alcohol which is present in wine or beer or liquor. You aren’t going to stop drinking beer or wine simply because it contains a different compound of the same element from anti-freeze, right? And yes, in large doses, methyl alcohol can kill you too.

        Now in terms of benefits and risks of vaccines, there are major differences between humans and cats. 1. The safety profile of human vaccines is far better, I doubt any human vaccine would be approved if it caused cancer in 1 out of 1000 or even 10000 humans except in case of a major epidemic of say a disease with extremely high mortality e.g. if smallpox came back. Smallpox vaccine could cause death in 1 in a million vaccinations, and some other serious adverse effects in some 250 of a million cases, but it was a whole lot better that 30% mortality of smallpox. Now, modern vaccines are a lot safer than smallpox vaccine was, but even a smallpox vaccine looks safer than cat vaccines.

        2. Cats are unique in their reaction to inflammation. As I mentioned any injection in cats especially those that result in more inflammation e.g. steroids or long-acting antibiotics can cause sarcoma. But as cats are vaccinated more often than give injections, you see more sarcomas after vaccines. But to minimize the risk the cats should be given only non-adjuvanted vaccines as they don’t cause chronic inflammation. But no injection in cats is 100% safe, there was for example a case or two of sarcoma at the site of microchip implantation. For that reason, you should only give injections to cats when absolutely necessary e.g. oral antibiotics are preferred unless there is really a need for an injection.

        3. Additionally, unlike cats, there are no indoor-only humans. I’d imagine that the risk of an indoor-only cat to be exposed to any of the diseases that we vaccinate against is a lot smaller than that of outdoor cats or for that matter humans.

        3. A lot of arguments of human anti-vaxxers is that their risk of dying from some diseases kids are vaccinated against is very small. But the whole reason they are small is because most people are vaccinated. When the majority of people are vaccinated, you get herd immunity i.e. you cannot catch the disease because everyone around you is vaccinated. But once herd immunity is lost e.g. if vaccinations fall below certain number (95% in some cases, a little less in others, a little more in yet others), your risk of catching these diseases and dying from them would go up.

        But let’s compare the risks e.g. from measles. If a child gets measles, his/her risk of dying is about 1 or 2 in a 1000 – from encephalitis or other complication, your risk of going blind is 1/10, risk of encephalitis in 1 in a 1000. Additionally, one can survive measles just fine, but develop encephalitis (SSPE) years later which would be fatal. Now, if you look at more serious risks from vaccine, you look at temporary issues like seizures in 1/3000 people, temporary low platelet count in 1/30000 people, and serious allergic reaction in 1 in a million people. More serious side effects are so rare that one cannot be even sure they are caused by vaccines. Incidentally, people often cite VAERS database for the side effects, but VAERS is self-reported with hardly any checks. For example, it contains entries like someone’s drowning a week after getting the vaccine. One woman wanted to check VAERS and reported that the vaccine turned her child into a superwoman, and they accepted it.


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