本题目来源于试卷: SL Topic C3.2 Defence against disease，类别为 IB生物学
[问答题]
f. Outline how the concept ofw,p /d-gx ;oqr herd immunity applies to mass vaccx8ax /)fj h2kcination against a d)xafcx8 kh/ j2isease.
参考答案: Herd immunity is achieved when a high percentage of individuals have achieved immunity. This helps to prevent the spread of an infection, even to unvaccinated people within the population. Herd immunity can be achieved by large scale vaccination programmes.
Herd immunity can also be achieved after a large proportion of a population have been infected by a disease, even without a vaccination programme.
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