An English physician, Edward Jenner, discovered that by inoculating a person with pustules from the pox infection of a cow, smallpox could be prevented.
一位英国医生爱德华?琴纳(Edward Jenner)，发现通过接种感染牛痘脓疱可以预防天花。
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He found that they'd all contracted a similar but milder disease, cowpox, which vaccinated them against the deadly smallpox.