VOA慢速英语:研究称俄罗斯的卫星V新冠疫苗似乎安全有效

dose – n. the amount of medication a person take at one time

placebo – n. a pill without medicine used in medical tests

immune – adj. resistant to an infection

variant – n. a different form of something

initially - adv. to begin with

publicity – n. notice or attention given to someone or something by the media