She explains that health workers have been using what I are called trivalent vaccins vaccines in some places.These are areas like Afghanistan where more than one kind of polio virus exists.是什么意思_She explains that health workers have been using what I are called trivalent vaccins vaccines in some places.These are areas like Afghanistan where more than one kind of polio virus exists.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句