To get at these non-mutating parts of the virus, Nabel and his colleagues used a two-step vaccination process, called "prime-boost."

VOA: standard.2010.07.21

I would first of all, congratulate you for taking the first step of starting to learn that process.

我会首先祝贺你踏出了学习语言的第一步，

学第二外语的时候 - SpeakingMax英语口语达人

This was done by Shimomura that was kind of the first step in this process of having it become such a useful tool.

这个工作是由Shimomura完成的,这是它成为一个有用的,工具的过程中的第一步。

麻省理工公开课 - 化学原理课程节选