VOA慢速英语:报告称穷国可能要到2024年才能接种疫苗

dose – n. the amount of a medicine, drug, or vitamin that is taken at one time

internal – adj. existing or occurring within an organization, such as a company or business

facility – n. something that makes an action, operation, or activity easier

non-binding (agreement) – n. an agreement that is not legally enforceable

bond – n. an official document in which a government or company promises to pay back an amount of money that it has borrowed

advance – adj. made, sent, or provided at an early time

herd immunity – n. a form of protection from infectious disease that happens when a large percentage of people have become immune, whether through previous infections or vaccination