目的大面积接种甲型肝炎（甲肝）疫苗，建立群体免疫屏障，控制甲肝周期性流行效果评价。
Objective To build the colony immune defence and to control the periodic epidemics of hepatitis A after a mass vaccination of live attenuated hepatitis A vaccine.
但是小麦条锈菌毒性变异频繁，可以通过变异产生新的毒性小种，导致小麦品种抗病基因失效，引起小麦条锈病周期性流行危害。
However, the virulence of wheat strip rust varied frequently and produced new virulent RACES which led to the breakdown of resistance genes and the periodical prevalence of wheat strip rust.
这同时在美国和其他地区成为替代货币的流行模式，即周期性的通过印花来交税，这样印花就能被花掉而不是被储存。
This was a type of alternative currency popular in America and elsewhere at the time that was periodically taxed with a stamp so that it would be spent, not hoarded.
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