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What is immunisation?

Immunisation is a way of creating immunity to certain infections.

Immunisation uses vaccines that contain relatively harmless antigens (molecules) that come from, or are similar to, the micro-organisms that cause the diseases. Micro-organisms can be viruses, such as measles, or they can be bacteria such as tuberculosis.  

Vaccines stimulate the immune system into reacting as if there were a real infection. The immune system then fights off the infection and remembers the organism so it has the ability to fight it off quickly if met again.  

Unlike most drugs, vaccines are given to healthy people so that they and the general population are protected from disease. Low immunisation rates and outbreaks of disease pose significant threats to the health of people who have not been protected and remain non-immune.

After clean water, vaccination is the most effective public health intervention in the world for saving lives and promoting good health. The term vaccination originated from the procedure used to protect people with the first vaccine for smallpox, vaccinia.

Visit  NHS Wales Direct (external link) for more information.