世卫组织说非洲将在三月份接受疫苗注射

dose – n. the amount of a medicine or treatment needed to treat a disease

income –n. money that is earned from work

surge –n. a fast increase in something

variant –n. something different in some way from others of the same kind

gene sequencing –n. a process that studies the order of DNA molecules to find out if organisms are related and to what extent

surveillance –n. to watch something very closely, especially to look for evidence of crime or disease

herd immunity –n. when enough people in a population can no longer be infected with a virus thereby protecting the rest of the people who are not immune from it