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Vaccination Programme Failure

AQA AS-level BiologyCell Recognition and the Immune SystemLesson 23 of 30

The efficacy of a vaccine is not always 100% and it may fail to induce immunity in certain individuals.

If individuals develop the disease immediately after vaccination their levels of immunity may not be high enough to prevent the disease and to prevent them passing on the disease to others.

Some pathogens, especially respiratory viruses such as Influenza viruses show antigenic variability. They mutate frequently so the antigens are suddenly no longer recognised by the immune system. This means immunity to the disease is short lived.

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Key terms in this lesson

pathogen
A microorganism, such as a virus, bacterium, fungus or protoctist, that causes disease.
antigen
A protein or glycoprotein, usually on a cell surface, that is recognised as foreign by the immune system and triggers an immune response.
T-lymphocyte
A type of white blood cell, matured in the thymus gland, responsible for the cell-mediated immune response.

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