Because no vaccine protects 100 percent of kids who get it, epidemiologists rely on "herd immunity" to make sure enough kids are well enough protected to keep a disease from spreading.

因为没有疫苗100%保护那些接种过疫苗的小孩，但流行病学家却根据“群体免疫”确信小孩能够很好地受到保护而防止疾病的传播。

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This is called herd immunity.

这就是所谓群体免疫力。

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Low 'herd immunity'.

“群体免疫性”低。

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And now vaccine resistance is spreading among parents who want to free ride on the herd immunity of others.

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No cattle vaccine is available, and one with the ability to provide near whole herd immunity is years away.

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All immunisation is intended to benefit the wider population as well as the individual through what is known as herd immunity.

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