VOA慢速英语:美国研究表明阿斯利康疫苗对各年龄段均有效

previous – adj. : existing or happening before the present time

excite – v. to cause feelings of enthusiasm in (someone)

confidence – n. a feeling or belief that you can do something well or succeed at something

inflammation – n. a condition in which a part of your body becomes red, swollen, and painful