If you look in Google Books you can find some of Jenner’s original papers. For example, there’s a collection of Scientific Papers; Physiology, Medicine, Surgery, Geology that includes Jenner’s three original publications. There’s also Jenner’s The Evidence at Large, as Laid Before the Committee of the House of Commons, Respecting Dr. Jenner’s Discovery of Vaccine Inoculation: Together with the Debate which Followed : and Some Observations on the Contravening Evidence, Etc which is pretty cool.