Below is a link to a more detailed history of vaccination, by Stefan Reidel, who is both an MD and a PhD. This particular story is relevant to Weeks 4 and 5. However, there is a general pattern: history gets fuzzy when we look closer.
Where the book (Killer Germs) suggests that Jenner heroically invented vaccination where before there was nothing, Reidel brings in the background that our text leaves out -- Jenner was important, but not the first to innoculate, nor the first to notice that cowpox conferred immunity to smallpox. However, he may well have been the first to put the two together, and he certainly was important in establishing widespread vaccination.
Actually, I find it deeply reassuring to know that innoculation was reasonably well established by Jenner's time. Otherwise, it would be unconscionable for him to test his idea by deliberately innoculating (i.e. infecting) a young healthy boy with cowpox, then later with smallpox to see if he had become immune.
Citation and Link
Stefan Reidel 2005. Edward Jenner and the history of smallpox and vaccination.Proceedings of the Baylor University Medical Center. 2005 Jan. 18(1):21-5. PubMed
Pay attention! Notice how I cited the article. You start with the Fantastic Four: author, year, title, source. This tells you who, when, what, how. How gives the journal, newspaper, book, or website that the article is included in.
After that, you get machinery that helps you find the article, including the link or URL.
Remember this for your papers: Fantastic Four + Machinery!