Biology for IGCSE & O level - Diseases And Immunity (Section 1 - No. 22)
What does the term 'herd immunity' refer to?
The immunity of a group of animals.
A form of passive immunity.
The protection against a disease when a significant portion of a population is immune.
The immunity gained from natural infection only.
Explanation
Herd immunity occurs when a high percentage of the population is immune, protecting those who are not.
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