Adjuvanted and Non Adjuvanted Vaccinations – Why should my cat be concerned?

September 04, 2014 / Cat's Meow / 24 Comments

Cats are a species that are unique in many ways. One of the more sinister of these is their tendency to develop injection site reactions. What this means is that when given certain types of injections, cats may react at the site of the injection, the type of injection that is most risky for your cat is an “adjuvanted vaccine”. This is a type of vaccine that contains an “adjuvant” or irritating chemical along with the virus or bacteria. These adjuvants are essential for some types of vaccine in order to boost the immune response and ensure protection. In humans, dogs, and other species they are quite safe and effective. In cats however, they have been implicated in causing “Vaccine Site Sarcoma” (VSS) a malignant and often fatal cancer. The risk of this occurring is extremely low, estimated between 1 in 10 000 to 1 in 30 000 cats. The most commonly implicated vaccine is “Killed” or “Adjuvanted” rabies, however some other types of injection (such as some long acting drugs) have also been found to cause these reactions.  

The risk of VSS is almost completely eliminated by the use of “Non-Adjvuanted Vaccines”. These vaccinations are specially formulated to eliminate the need for an adjuvant and allow for safe inoculation with little to no risk of tumor formation and are just as effective as their Adjuvanted counterparts.  

Here at the Village Cat Clinic, we are proud to use ONLY non-adjuvanted vaccines in all our patients. We also avoid the use of any other drugs known to cause injection site reactions. Though these vaccinations are  more expensive than the adjuvanted versions, we strongly believe in providing only the best quality of care for our patients. 

Come talk to our knowledgeable staff and doctors at any time with questions or concerns you may have about vaccines in cats.
Written by Dr.Matthew Kornya

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Hi Carol Thank you for reading out blog post.  I wouldn't necessarly say "most" as I don't have any actual stats to answer you with.  I would feel comfortable saying a significant number of vets are still using them.  They are much cheaper to purchase for the veterinary clinic.  Your best bet is to ask what they are using.  The only non-adjuvant vaccines currently on the market are still the Purevax line. 

Posted by Angelina Johnstone on May 23 2019 @ 5:29 pm

Are most vets giving adjuvant end vaccines? And why?

Posted by Carol Santa Barbara on May 23 2019 @ 5:09 pm

Thiomersal is a commonly used preservative in vaccines. It is an "organomecury" compound, which means it does not have the toxic effects associated with inorganic mercury. It is more commonly used in multi-dose vials of vaccine and is not present in the single-dose vials commonly used in feline medicine. The vaccines we use at The Cat Clinic do not contain thiomersal; however the WHO considers thiomersal in vaccines to be safe and there is no evidence that it poses any risk to cats, dogs, or humans. It is not associated with Feline Injection-Site Sarcoma.  Dr.Matt Kornya

Posted by Angelina Johnstone on April 2 2019 @ 4:25 pm

I would like to know if thimerosal in vaccine formulations is a problem for cats! Thanks for the attention!

Posted by Cybelle on April 2 2019 @ 10:42 am

Hello Jacqueline The only non-adjuvanted vaccine that I'm aware of on the market in Canada is Purevax which was by Merial (they were bought by Boehringer Ingelheim) They have both a 1yr and 3yr Rabies, a Feline Leukemia, and a FVRCP vaccination.  We have used Purevax exclusively for many years. I'm not sure who the veterinary supplier is in BC but there are two board certified feline specialists in BC I'm sure if you called one someone on their teams could tell your veterinarian the purchasing information.  In Ontario we have central warehouses for all of our supplies instead of ordering from the individual companies. Dr. Elizabeth Ruelle owns Wild Rose Cat Clinic of Calgary and Dr.Diane McKelvey is currently practicing at Aberdeen Veterinary Hospital in Kamloops. For your Feline Leukemia question.  Because of there is no treatment for Leukemia, and there is always the risk of escape or bringing in a new pet and Hamilton (our area) has known Feline Leukemia in our stray population we vaccinate all of our patients for Leukemia initially and then booster at one year.  After that we decide on a case by case bases based on the individual risks.  There is a guideline that can be found on the Cat Healthy Canada site at This recommendation may be slightly different in your area.

Posted by Angelina Johnstone RVT on March 30 2019 @ 12:35 pm

Hi I am in BC and am having a lot of difficulty finding a vet that has non-adjuvanted vaccines. I have been told that it is not legal in Canada. that they find it hard to believe that rabies vaccine would be done that way due to the dangerous associated with the disease. Can you help me find a supplier that can provide my vet with a non-adjuvanted rabies vaccine for my kittens. Also, My kittens were tested and are negative for feline leaukemia, they are indoor cats but there is always a risk they can get out. should we vaccinate them for feline leaukemia. If so we will be looking for a non adjuvanted vaccine for that also. Thank You for your assistance

Posted by Jacqueline. M. on March 29 2019 @ 7:42 pm

I am just finding out about overvaccination, and risks to the site, esp. the ones that are adjuvanted, so I called around to local vets and every receptionist, without exception, had no idea what I was talking about. Wouldn't you think they'd be a little informed??? I'm appalled that I never looked into it myself, but apparently that's quite common, even in those who work for vets.

Posted by Susan Paradis on February 4 2019 @ 10:12 am

Hello Kris Thank you for reading our blog.  This will be something you should discuss with your veterinarian as it will depend a lot on your cats lifestyle and where your located.  Studies do show that the last FVRCP vaccination should be done after 16weeks in most cases.  Your veterinarian is going to be your best source of information.  Please note that the vaccination you mentioned in your other post is not a non adjuvanted vaccination.

Posted by Angelina Johnstone on September 4 2018 @ 9:14 am

I recently lost my abyssinian at 14 years to lymphoma. I am concerned about over vaccinating my new Aby kitten . She's an indoor only cat home, should I at least consider feline leukemia in addition to her core vaccines?

Posted by Kris Steuter on September 1 2018 @ 5:22 pm

My kitten had Nobivac at 5 and a 1/2, 9 and 14 and a 1/2 weeks. The vet wants to repeat the 3rd Nobivac because it was done before 16 weeks and do another booster a month later.. Seems to me that's over vaccinating. Advice?

Posted by Kris Steuter on September 1 2018 @ 5:20 pm

Hello Ondine in general the choice of a one year  Rabies vaccine or a 3 year Rabies is a conversation to have with the doctor and is decided on an individual bases depending on the needs of that patient.  In general the first year a kitten is going to get a series of vaccinations  part of this series needs to be boostered after one year (FVRCP) regardless of which Rabies vaccination you choose.  More importantly please keep in mind that the examination (consultation) is one of the most important parts of a cats annual visit so even when they are older and the annual visit time falls on a year where they are not getting an injection they still should see the doctor for the examination.  We go to our doctors every year and our cats age even more rapidly and are masters at hiding problems so skipping the exam even if it sounds like it's saving you money probably won't in the long run. For more information about vaccination protocols please check out

Posted by Angelina Johnstone RVT on August 15 2018 @ 4:53 pm

Why do cats seem to always be vaccinated against rabies with a 1-year vaccine for the first time? Can a cat (over 12 weeks old) be instead vaccinated for the first time with a 3-year Purevax recombinant rabies vaccine? The problem with the 1-year vaccine is that owners may not want to incur the expense of a consultation and office visit at the vet again just a year later for rabies. Wouldn't a first time 3-year recombinant vaccine be more economical for owners (1 office visit in 3 years instead of 2 a year apart)? Thank you!

Posted by Ondine Hasson-Duphil on August 14 2018 @ 11:15 pm

Hello Nicholas Purevax Rabies vaccine comes in a 1 year and a 3 year version so it depends on which one the clinic is using.  Even if they are using the one year and the kitty is getting vaccinated every year with a non-adjuvanted vaccine it is still safer than getting a adjuvanted rabies every three years.  

Posted by Angelina Johnstone on June 19 2018 @ 11:50 am

I was told that adjuvanted rabies vaccines in cats last 3 years, whereas the non adjuvanted ones need to be given every year. Is this true? Thank you.

Posted by Nicholas Galante on June 16 2018 @ 1:36 pm

Thanks for being so careful with the kitties in your charge. I live in Illinois, but I was just researching non adjuvanted vaccines and saw you don't use them. 😃

Posted by Sarah Hance on September 17 2017 @ 10:13 am

Hello Mary Purevax is made by Merial and are available in several combinations including FVRCP.  You can find information on them at They are currently the only non-adjuvanted vaccination on the market.

Posted by Village Cat Clinic on August 8 2017 @ 9:00 am

We are sorry to hear about your loss Caroline.  Loosing a family member is never easy.  In Canada we also rotate vaccinations based on risk. 

Posted by Village Cat Clinic on August 8 2017 @ 8:55 am

After losing a kitty to VSS, I was terrified to vaccinate again. Thank you for the wonderful information! I feel comfortable choosing a non-adjuvanted vaccine after reading this.

Posted by Lydia on August 7 2017 @ 5:51 pm

Do I understand correctly that there is a non-adjuvanted injectable FVRCP vaccine?

Posted by Mary on August 7 2017 @ 11:08 am

Thanks for the brief understandable article. Cat owners are not warned of this in the UK., which means no alternative to the adjuvant is offered. No cattery will care for an unvaccinated cat. My cat was PTS on Saturday. A lump on her shoulder blades was noticed in late April. The operation was horrendous (20 staples and 20 stitches) in what I consider an unnecesary attempt to prolong her life by reducing the spread. The vet did not check for other growths before he operated or he would have see n what I did as she lay under sedation prior to the op: her abdoment and paws were covered with swellings. Had I known I would not have put her through a useless op. I loved her too much for that. I believe we should be informed of this. Our choice would be risk of cáncer or risk of vaccine not fully working. For an indoor cat (for special reasons) the letter would be a better option as the cat is less at risk of contagious infections.

Posted by Caroline Graham on July 10 2017 @ 8:42 am

Rabies is the only vaccination i will b allowing for my 8 yr old indoor cat. And i will get a non-adju anted, no kill shot. Merial is the manufacturer of the 3 yr rabies shot. Am i correct w/this information? Ty!!

Posted by Kari on September 18 2016 @ 10:04 pm

Thanks for the info, I just adopted a kitten, and was reading pamphlets from the Vet. Thanks

Posted by Paul on June 8 2016 @ 7:39 pm

Hi Holly,   I've spoken with one of our Doctors and he has recommended giving us a call or stopping by the clinic to have a discussion about this. He would like to have a bit more information about your kitties and their situation before dispensing any medical advice. While FeLV vaccinations are quite effective if given on the proper schedule, FeLV is a contagious and fatal disease, so conversation around this subject will be essential.   

Posted by Angelina Johnstone RVT on May 26 2015 @ 10:35 pm

Hi there! I have six year old sibling cats that were not vaccinated as kittens for feline leukemia. I switched vets later on and the cats were given the felv vaccine for the first time last year. I have a felv positive cat who will soon be integrated into our home with the healthy cats. I am looking for advice on the best course of action at this point in terms of vaccinations. Are my cats more suceptible to the virus since they weren't vaccinated as kittens? Should I start a new series?

Posted by Holly on May 17 2015 @ 10:24 am