What were some qualities that Edward Jenner had that led him to investigate the relationship between smallpox and cowpox?

I read the other day, that one of the signers of the Declaration wrote a book saying African Americans could not catch catch Yellow Fever. Because everyone believed him, many negroes of the time, did not move. They stayed in Philadelphia and died. Absalom Jones took care of many sick people and it is thought he would be remembered today for this huge act of bravery alone. I hope that helps.