The clinical trial was designed such that almost two million elementary school children were given this test vaccine.

该临床试验的计划是,向近二百万的小学学生,接种这种测试疫苗

耶鲁公开课 - 生物医学工程探索课程节选

They did this in 1,800 elementary school children, so these are about eight year-olds.

于是科研人员给一千八百名,八岁左右的小学生分发疫苗

耶鲁公开课 - 生物医学工程探索课程节选