If this was tetanus, you got this tetanus vaccine when you were young; you get a boost every five or ten years because your antibody levels are starting to fall.

以破伤风为例,小时候,你接种过破伤风的疫苗,每隔五年或十年要再接种一次,这是因为体内的抗体浓度会下降

耶鲁公开课 - 生物医学工程探索课程节选

Let's say you want to see how something like cigarette smoking is changing in the population and the rates of cigarette smoking, and you want to look at people every five years from 1970 to 2000.

比如你想知道,人群中吸烟者的人数变化,和吸烟者的比例,在1970年至2000年每五年的情况

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选