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:

MANUFACTURING

Inactivated – more complicated and expensive to manufacture.

Live – easy to manufacture.

SAFETY

Inactivated – safe

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

STORAGE

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.

PREGNANCY

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.

VIRULENCE

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.

IMMUNITY

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)

BOOSTER DOSE

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