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Livestock production: The difference between antibiotics and vaccines

Question: Do antibiotics and a vaccination work in the same way?

Antibiotic treatment and vaccination are totally separate approaches to disease control and must not be confused.

To understand the difference, you have first to understand how an animal’s body protects itself naturally, without the help of an antibiotic or vaccine.

  • Animal bodies consist of millions of different kinds of cells which form the building blocks for all parts, such as the organs, skin and muscles.
  • The body has a system which enables it to recognise each of these cells as its own.
  • Any foreign cells – such as disease-causing bacteria (germs) – that enter through the skin or the lining of the intestines, are identified as a foreign substance, or invader.
  • The body’s defence system is immediately activated and will try to destroy the bacteria before they invade and damage the animal’s own body cells.
  • The defence system consists mainly of different types of white blood cells in the blood and lymphatic system.
  • Big white blood cells “eat” some of the bacteria circulating in the blood.
  • Inside the white blood cells the bacteria are broken into pieces, each of which bears a specific code.
  • The defence system now forms specialised white blood cells that will recognise this code. These special cells travel throughout the body, via the blood stream, to catch and destroy any bacteria that carry the code.
  • The process of recognising “foreign” bacteria and making the specialised white blood cells needed to destroy them, takes about a week.
  • It takes another week to search for and destroy these bacteria wherever they may be in the animal’s body.
  • During the time the body takes to build up a defence against a new invader, the bacteria will have continued to multiply and destroyed many cells, causing severe damage to the normal functioning of the body.
  • In many cases the animal dies before the defence system is ready to protect it.


  • When bacteria invade the body of an animal and the defence system is activated, it causes a fever reaction.
  • The animal starts showing signs of disease such as eating less and looking dull or depressed – for example, hanging its head when it is standing.
  • If an antibiotic injection is given, it will go into the blood and then into the whole body. Antibiotics are medicines that kill specific types of bacteria.
  • So, while the animal is busy activating its own defence system, the antibiotic immediately starts killing the bacteria destroying cells and causing damage.
  • In effect, an antibiotic supports the body’s defence system by immediately starting to kill invader bacteria.


  • Some diseases, such as pulpy kidney, kill so fast that there is no time to use an antibiotic. And antibiotics cannot kill viruses (another type of germ causing diseases such as lumpy skin disease).
  • The only way to control these diseases is to vaccinate the animal.
  • A vaccine is manufactured from the same germs that cause a disease, but these are killed or changed in such a way that the vaccine will not make the animal sick.
  • The body’s defence system is activated after the vaccine has been injected, and forms white blood cells and antibodies against the bacteria or viruses in the vaccine.
  • Because the germs in the vaccine don’t damage the body, the affected animal develops a defence system against the specific germ, without affecting the working of the body.
  • Whenever the animal is exposed to the same disease in future, its body will be ready to defend it within 1 to 2 days and will destroy the germs before they can cause damage to the cells, organs or bodily systems.
  • Vaccinations, therefore, are only used for healthy animals, to prevent disease at a later stage. They are not used to treat already-sick animals, as antibiotics are.
  • Stock must be vaccinated every year against pulpy kidney (sheep and goats), botulism and black leg (cattle).

Also read:
Livestock production: How vaccines work against diseases

  • This article was written by Dr. Danie Odendaal and first appeared in Farming SA.

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