How do vaccines work?

Vaccines work by training the immune system to produce antibodies to certain micro-organisms, just as we do when we are exposed to an infection – but with the advantage that we do not develop the disease.

Vaccines contain inactivated or attenuated micro-organisms that, when they enter the body, ‘trick’ the immune system into thinking it is under attack by a pathogen. This causes the body to generate a specific immune response against the micro-organism(s) in the vaccine, but without having to suffer the effects of the disease.

Most vaccines generate long-term immunological memory. This means that when the person comes into contact with the natural infection in the future, the immune system has already been trained to recognise the micro-organism and produce antibodies to prevent the disease. In general, several doses of vaccine, spaced out over time, are usually necessary to obtain an adequate immune response.