Smallpox vaccine, the first successful vaccine to be developed, was introduced by Edward Jenner in 1796. He followed up his observation that milkmaids who had previously caught cowpox did not later catch smallpox by showing that inoculated cowpox protected against inoculated smallpox.

First unfound claim:

Smallpox vaccine, the first successful vaccine to be developed, was introduced by Edward Jenner in 1796.

Why was it successful?
Because of a second unfounded claim:

"by showing that inoculated cowpox protected against inoculated smallpox"

Any sources that back up this claim?

Also the second paragraph which deals with inoculation NOT vaccination I have to research their statistics and understand exactly how they derived them and from what populations, so wait for the follow up.
As it stands vaccination and inoculation are synonyms yet one bypasess (vaccination) the mucus barrier and another does not, so how is that the same thing? It isn't.