World Immunisation Week

Vaccinations save millions of lives every year for both people and animals.  They have enabled some really dangerous diseases to be eradicated completely (smallpox in people and rinderpest in ruminants) and have reduced the disease and mortality associated with many others.  However, over recent years, reduced levels of vaccination due to concerns over side effects has led to re-emergence of many of these diseases.

The immune system

Diagram of antibodies latching onto antigenThe immune system is a complex interaction of cells and proteins which protect the body from attack by disease-causing organisms (pathogens) such as bacteria and viruses.  White blood cells are the main cells involved, some of which produce antibodies, small proteins which latch on to parts of the pathogen known as antigens to prevent them from attacking the body’s cells.  Other white blood cells surround the clumps of antibodies and pathogens and digest them.

When a pathogen which has not been encountered before enters the body, the white blood cells will start to produce antibodies against it.  However, this takes time and the pathogen will normally cause the disease before the body gets on top of it.  Depending on the disease, this may be fatal before the body produces enough antibodies to neutralise it.  If recovery occurs, the body will keep some antibodies in the circulation, and also ‘memory B cells’ which are able to produce massive amounts of antibodies very quickly if the same infection occurs again.  This means that the pathogen is likely to be neutralised before it causes disease.

What is vaccination?

Tabby cat having an injectionAt its most basic, vaccination is the administration of a weakened or dead form of the disease-causing organism (most often a virus) which causes the body to mount an immune response, without the risk of the disease occurring.  The memory of this immune response remains once the vaccine organism has gone, allowing the body to quickly respond if the real organism comes along before it has a chance to cause disease.  The duration of this immune memory depends on the vaccine, which is why regular ‘booster’ vaccines are needed against many diseases, to keep this memory alive.

Vaccinations are most commonly given by injection, although they may also be administered up the nose (kennel cough and children’s flu vaccines), or by mouth (polio vaccine).

What are the side effects of vaccination?

German Shepherd lying down looking anxiousSevere side effects of vaccination are extremely rare.  Mild side effects are more common and are an indication of the immune system responding to the vaccine.  These can include:

  • a small lump in the area of the injection
  • a fever
  • reduced appetite
  • lethargy

These mild side effects normally last 24-48 hours, also a lump can stay present for a couple of weeks.  They do not normally require any treatment, although some animals and people may benefit from an anti-inflammatory medication to settle the high temperature.  These side effects are nothing to worry about and are negligible compared to the disease caused by the real pathogen.

Severe side effects can occur due to an allergic response to a component of the vaccine (for example some human flu vaccines are egg-based which can cause problems with people with egg allergies).  Allergies to vaccine components in animals are very rare.  Signs of a problem will normally occur very quickly (before you have left the surgery) and will need immediate treatment.  If your pet is allergic to a vaccine, they may be able to receive a different brand in future, or they may need to be left unvaccinated, in which case they are reliant on high levels of vaccination in animals around them to keep them safe.

What about immune-mediated disorders?

Border Collie with grassy backgroundSome people believe that immune-mediated disorders such as haemolytic anaemia and polyarthritis are caused by vaccinations but the evidence is lacking of a cause-and-effect relationship.  These disorders can be stimulated by anything which affects the immune system so while theoretically vaccination could be a potential trigger in dogs with a genetic predisposition, illnesses are just as likely to be a trigger factor, and in many cases there is no obvious cause and they just happen spontaneously.  These are rare diseases in any case and un-vaccinated animals appear just as susceptible.

Why should I get my pet vaccinated?

3 Maine Coon cats lying down, 2 Tabby, one ginger and whiteVaccines save lives.  If you want to keep your pet safe, get them vaccinated.  Having your pet vaccinated will also help to protect other animals around them.  Herd-immunity is the term used when a sufficient number of animals are vaccinated that the level of virus around is low, and therefore protects the few animals around who are unable to be vaccinated (e.g. young puppies, animals on immune-suppressive medication, or those with allergic reactions to vaccines) or who for some reason do not respond to vaccination.

Can’t I use homeopathy instead?

At first glance, vaccine and homeopathic nosodes may appear to be similar.  They are both based on administering a small amount of the substance that causes disease in order to protect against that same disease.  However, whereas vaccines use a very measured portion of an inactivated form of the pathogen, homeopathic nosodes are made from a specimen such as saliva, pus, urine, blood or diseased tissue from a diseased patient.

This specimen is then diluted so much that not a single molecule of the original substance remains (i.e. it is just water).

Nosodes have been shown to have no effect on antibody levels against diseases and therefore are not a substitute for vaccination.

Related pages

Dog vaccinations

Cat vaccinations

Rabbit vaccinations

Further reading

World Small Animal Veterinary Association vaccination guidelines

British Small Animal Veterinary Association position statement on vaccinations

A randomized, blinded, placebo-controlled trial comparing antibody responses to homeopathicand conventional vaccines in university students.

Veterinary Medicines Directorate position paper on vaccines for dogs

National Office of Animal Health vaccination overview

World Health Organisation – World Immunization Week

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