A vaccine contains a dead or weakened form of a pathogen (or its antigens). It triggers the immune system to produce antibodies and memory cells without causing disease. If the real pathogen enters later, memory cells respond rapidly.

Why don't vaccines cause the disease they protect against?

Vaccines use dead or inactive pathogens, or just antigens from the pathogen's surface. The pathogen cannot multiply or cause infection. The immune system still recognises the antigens and builds immunity.

Sample Questions

What do vaccines contain?

A. Live, active pathogens that cause disease
B. Dead or inactive pathogens or their antigens
C. Antibiotics to kill bacteria
D. White blood cells from another person

1 markfoundation

Explain how vaccination protects a person from getting a disease. [3 marks]

3 marksstandard

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