The vexing question – Killed vaccines vs Live vaccines

8 September, 2006

1. To vaccinate or not?

The kittens are coming up to nine weeks, and according to veterinary protoccol, they should be vaccinated at nine weeks and a secondary vaccine at twelve weeks.

I’m not entirely happy about this. From a holistic perspective, vaccines stress/alter the immune system, they do not confer immunity – their merely ameliorate the symptoms of the illnesses being vaccinated for. There is even a school of thought that believes that because certain illnesses have been “eliminated” through vaccination, it’s given rise to other illnesses. Furthermore, kittens get immunity from their mother’s milk up to the age of 14 weeks – surely that would cancel the vaccination out?

However, I’ve heard of cases of cats dying from illnesses because they haven’t been vaccinated. So: the jury is still out on not vaccinating, and I will vaccinate because it’s the cat association’s guidelines and I still haven’t the guts to put my foot down and be 100% holistic, because of “what ifs”.

2. 3-in-1 vaccine or 5-in1 vaccine?

The core vaccinations are for feline infectious enteritis (panleucopaenia) virus, feline rhinotracheitis virus and feline calicivirus, i.e. 3-in-1 vaccines. Some pharmaceutical companies have come up with 5-in-1, with the addition of chlamydia and feline leukaemia.

I think a young kitten’s immune system is too immature to cope with a 5-in-1.

FeLV is a serious, often fatal illness. It’s transmitted via blood or saliva or sexual intercourse. It’s something to consider if cats wander the streets.

My cats do not wander the streets and meet other cats – they are kept in a confined garden. My mother cat has been tested negative for FeLV.

Recently I’ve heard rumours of severe reactions to 5-in-1 vaccines – a kitten was permanently blinded after such a vaccine.

So: 3-in-1 vaccine.

3. Killed vaccines or live vaccines?

My vet has given me a choice: Norbivac Tricat which is a live attenuated (i.e. modified) virus, and Fevaxyn iCHP which is a killed (i.e. inactivated) virus.

There are arguments both for and against live vs. killed vaccines.

Modified live vaccines typically stimulate broader immune response.They are sufficiently weakened (attenuated) to avoid causing disease. However, modified live vaccines are considered the most dangerous by experts in immunology. They have the ability to replicate and then mutate in the body and are banned in Scandanavian countries. In multi-cat households, there is the risk of the virus being shed and causing illness in other cats.

So, a killed virus should be safer, right? Unfortunately, killed vaccines take longer to stimulate an immune response. In most killed vaccines, adjuvants (chemicals) are added to stimulate the immune system. Although adjuvants improve the effectiveness they also increase the risk of reactions, e.g. swelling near the injection site, and sometimes tumours. I’ve read that in the US, vets are advised to vaccinate on a limb of the pet so that if a tumour does develop, the limb can be amputated. Sheesh … what are we doing to our pets?

Last year I vaccinated using a killed 3-in-1 vaccine. So maybe I’ll stop dithering and use the same.


9/3/09 – Further thoughts on vaccination based on the comments that have been left on this post.

— There is always a risk in vaccinating young kittens.  I still haven’t resolved this dilemma yet.

— Don’t try to do too much at once, i.e. vaccinate, plus de-worm plus de-flea at the same time.  Young kittens’ systems can’t cope with this much chemical overload.

— I usually de-worm at least a week before vaccination because I’ve read somewhere that worm die-off and toxicity can make a kitten’s body more vulnerable to vaccinations.



  1. I just had a 12 week old kitten that was healthy & vibrant and died of panleukemia after receiving his “shots”. The Vet tech gave a modified live virus instead of killed

  2. Dear Kimberly,

    That is terrible news. I am so sorry about your poor kitten’s death. I don’t know what else to say except I hope it never happens again to you. Please don’t blame yourself … you only did what you thought was right.

    It would be very helpful if you could let me know whether it was it a 3-in-1 or a 4-in-1 or even a 5-in-1? Do you know which vaccine it was (i.e. which brand, e.g. Fort Dodge etc.). Find out if your vet is will submit a report to the company that manufactured the vaccine – I think in the UK it is standard procedure.

    Also, if you are a member of any breeders’ forums or even a cat site, please post the information. The more people who share this information, the more it could help other kittens out there.

    Thinking of you during this difficult time.

  3. no website, just generally interested, would like to help, live in luton, beds, uk, people are killing their kittens. I am on benefits, so therefore not welloff, however, my kitten that I rescued, was not what, anyone would rescue, leaky eyes, underweight, mother had died, he smelled, not sure if he would of lived, but my son, likes to believe even the runt of the litter has a chance. Now, the problem, we couldn’t afford the vaccinations, however the cat hasn’t been out and completely looked after, he wasn’t well when we got him, but now fine, and very good looking cat, we are so proud, however, we are not so well, we have never been ill in our lives, and both of us have been on antibiotics, with no success, what do you think the possiblity is that we have become ill through, either the previous owner, or the cat flu. Do not wish to bother the DR with this info, cause it seems silly.

    • Dear Hayley,

      Many thanks for your post, it’s amazing what you’ve done for the kittens. Most people wouldn’t have taken on a sick kitten.

      To be honest, I wouldn’t vax a sick kitten, and even now that he’s recovered, I wouldn’t vax until he is really really healthy, and if he is an indoor-only cat, without any exposure to any other cat, then I don’t see the need to vaccinate.

      I’m so sorry that you and your son aren’t well. To the best of my knowledge cat diseases are not transmissible to humans. I will check with my vet just to make sure. But as far as I know, it is not possible to catch a cat illness.

      However, there are a lot of bugs going round at the moment – the flu bug, and the vomiting (norovirus) bug. It is possible that you have got one of them. Plus if you’ve been devoting your time to looking after the kitten it is possible that your immune system has got run-down. Antibiotics are not the cure-all. They can only kill bacteria and not viruses. So if you have a cold, antibiotics won’t kill the cold/flu virus. Antibiotics are usually given for the secondary infections that an immune system (depressed by a virus) gets. It could be that you need a different antibiotic – maybe it’s not working. But it may just be a case that your immune system is run-down and you need to build it up again by getting plenty of rest and eating well.

      Good luck and best wishes to you and your family.

  4. We recently (10 days ago) vaccinated 8 wk old kittens with a 3 in 1, killed virus vaccine. We also administered Pyrantal for worming and kitten dose of Revolution. As of yesterday, there is only 1 kitten left of 4.

    They appeared healthy with clear eyes and respiratory systems at the time we did the administering of the vaccinations.

    Can you provide any direction on why they may have died?

    Thank you!


  5. Hello Louise,

    I’m so sorry about the loss of your kittens. This is such bad luck and really heart-wrenching when it happens.

    Some of the questions that breeders may ask to work out why it may have happened are:

    — when did you deworm the kittens? Was it at the same time as the vaccinations? Most breeders deworm their kittens 1-2 weeks’ before the vaccination. This is because any toxins caused by the worms dying from the worm medication may affect the physical condition of the kittens and reduce their ability to cope with the vaccine. So by giving at least 1-2 weeks before the vaccination, it gives the kittens’ systems a chance to deal with the worms and then regain strength. Also, and I don’t know how true this is … but I’ve heard that if you vaccinate without deworming, this can cause the worms to affect the kittens’ health.

    — when did you administer Revolution? Before the vaccination? How soon before the vaccination? Unless absolutely necessary, breders don’t administer flea medications to young kittens.

    — why did you vaccinate at 8 weeks? Is this based on the vet’s recommendation? In the UK, breeders vaccinate at approx. 9-10 weeks and then again 3 weeks’ later. 8 weeks could have been too early for the kittens.

    With kittens it may be necessary to be careful how much is administered, what combination and when. For e.g. vaccination plus worming plus flea medication could be too much of a chemical overload for young kittens. i.e. don’t too much at once. Kittens are quite fragile creatures and you don’t want to overload their systems with chemicals.

    There are forums on the internet, with experienced breeders and vets who may be able to answer your questions better:



    In the meantime, I hope that your remaining kitten survives. I will say a prayer for your kitten.

  6. I have been breeding persians for over 10 years and I use the 3 in 1 ultranasal vaccination at 12 weeks of age. The instructions state to vaccinate once at 12 weeks of age. I have never had a problem. http://www.revivalanimal.com/Feline-Ultranasal-FVRCP.html

    • i used that vaccine and my kitten got a terrible uri that took months to get rid of another breeder I talked to had the same experience

  7. Can you provide a reference for this:
    Modified live vaccines typically stimulate broader immune response.They are sufficiently weakened (attenuated) to avoid causing disease. However, modified live vaccines are considered the most dangerous by experts in immunology. They have the ability to replicate and then mutate in the body and are banned in Scandanavian countries. In multi-cat households, there is the risk of the virus being shed and causing illness in other cats.

    I am curious about other cats getting sick in a multicat household. thank you!

  8. I always take my one-year old Persian cat to his vet for check ups. I only wanted her to do deworming to my cat but she always insists to vaccinate him. I am aware about the side effects of vaccines, especially the rabies vaccination, and I think that it can harm my cat and I am really terrified about it. But my cat stays indoors and I never let him wander around. He doesn’t even interact with other animals. Should I take the vet’s advice or not?

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