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[2019年上半年VOA常速英语] VOA常速(翻译+字幕+讲解):美国卫生部规劝父母为孩子注射麻疹疫苗
Doctors recommend that children get two doses of the vaccine. The reason that we give a second dose is because about 5 percent of children do not respond to the first dose, so with two doses, over 9..2019-02-19 编辑:Emma