I think it's generally accepted these days that T1D is an auto-immune response; our immune system gets stimulated by an external pathogen and mistakenly identifies the Islets of Langahans (beta) cells in our own pancreas as the same pathogen. The resulting immune response successfully destroys the mis-identified cells along with the dangerous stuff.
See the 'Virus' sub-heading in the Wikipedia article:
The article is confused, because the currently accepted 'antibody' test implies that medics believe description I gave is correct; there might be any number of possible pathogens and not all the things our immune system reacts to are viruses (bacteria for example.)
Anyway, a vaccine is a dead, or non-functional, pathogen that provokes the immune system to produce the stuff required to destroy even a functional (dangerous) version of that pathogen.
Therefore, by definition, a vaccine 'against' T1D would actually *cause* T1D, assuming that T1D is caused by an auto-immune response.
If the T1D auto-immune response is caused by a single pathogen then developing a vaccine that promotes an immune response which does *not* attack our own bodies would be an effective way of avoiding T1D: it does *not* prevent it, it avoids it by avoiding the sequence of events that would otherwise case it. It isn't a vaccine against T1D, it's a vaccine against something else that, as a side effect, lessens or eliminates the possibility that a particular one of us might develop T1D.
The JDRF article is here:
What they are trying to do is *not* develop a vaccine; it is to come up with a methodology that causes the immune system to generate alternative attack paths for the pathogen. Unfortunately lack of originality seems to have prevented their marketing man [Richard Insel] from coming up with a term other than "vaccine".
In the end, however, it comes down to persuading our own immune system that our own bodies are not the problem without, simultaneously, persuading the system there really is no problem at all; AIDS prevents diabetes.