The difference between live and inactivated vaccines

Question:  What is the difference between live and inactivated vaccines?

  • Vaccines are divided into 2 groups, live (attenuated) and inactivated vaccines.
  • Vaccines consist of antigens. Antigens are viruses, bacteria, protozoans, fungi or toxins and can be inactivated (dead) or live.
  • More recent vaccines can even consist of small pieces of antigen only.
  • When the antigen is injected into an animal or human, it stimulates the immune system and antibodies against the antigens are produced.
  • Antigens are usually inactivated (killed) by adding formalin.

Below is a comparison between inactivated and living vaccines:


Inactivated – more complicated and expensive to manufacture.

Live – easy to manufacture.


Inactivated – safe

Live – can be dangerous for applicator if person injects himself, e.g. anthrax and contagious abortion (brucellosis) vaccines.


Inactivated – less critical

Live – handling is critical. Cold chain (4°C to 8°C) must always be adhered to. Short periods outside the fridge can destroy the antigen. The exception is anthrax, which is in spore form.


Inactivated – safe for all pregnant animals.

Live – some live vaccines should not be administered to pregnant animals because it could cause abortions. Read leaflet for instructions.


Inactivated – the antigen is inactivated. Cannot return to virulence (causing illness).

Live – There is always a possibility that the antigen can return to virulence and cause disease.


Inactivated – immunity takes longer to develop and can be of short duration.

Live – immunity develops quickly and can have a longer duration (sometimes life long)


Inactivated – needs a booster dose, except when indicated otherwise. For example, pulpy kidney with oil adjuvant.

Live – needs no booster dose.

There might be exceptions, so it is important to study the package leaflet thoroughly before application. Consult your vet for any queries.

  • Compiled by Dr Faffa Malan, veterinary consultant

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