Conversation so far:
When did Jonas Salk start doing polio research?
1948
What was the first part of Jonas Salk's polio research?
Harry Weaver, director of research at the National Foundation for Infantile Paralysis, asked Jonas Salk to find out if there were more types of polio than the three then known.
Did Jonas Salk find out if there were more than three types of polio?
What did Jonas Salk discover in his polio research?
In 1954 Jonas Salk tested the vaccine on about one million children, known as the polio pioneers. The vaccine was announced as safe on April 12, 1955.

Question: When did the first person get the vaccine?
Self-contained rewrite: When did the first person get the polio vaccine?