The levels of antibody in the blood decline over time following both natural infection and vaccination. But even though antibodies disappear, immune memory persists. Most vaccines produce immune memory that lasts a very long time, if not for life. But others, for example diphtheria and tetanus toxoids, must be repeated every 10 years to maintain adequate levels of protection. These are called boosters. The presence of immune memory means that the immune system can respond very quickly, to either infection or a booster dose of vaccine. When a booster is given to a person who already has immune memory (perhaps from a previous booster), the immune response is much faster and stronger than when a booster is given to a person with no immune memory.

This document was published by the Canadian Paediatric society, 1997.

Posted by the Canadian Paediatric Society, July 1997.

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