We hear about vaccines in the media and most of us have had them at one time or another during our lives, but what exactly are they?

In its simplest sense, a vaccine is a biological preparation used to help prevent an illness by increasing immune resistance to it.

There are different types of vaccine, depending on the type of pathogen causing the illness and how it causes disease. Some are given just once during a lifetime and some are given multiple times as ‘boosters’ to protect during times that the individual might be susceptible to the illness.

After clean water, vaccines are the most effective way of preventing infectious diseases1. Bacterial meningitis and septicaemia are examples of diseases where vaccination can truly be the difference between life and death or life-long disability.

1. Plotkin SL, Plotkin SA. A short history of vaccination. In: Plotkin SA, Orenstein WA, eds. Vaccines, 4th edn. Philadelphia: WB Saunders; 2004: 1-15.