There are reasons they are only developing for CD. But the picture is complicated.
The UC<-->MAP research so far has been inconsistient However, something may be learned about
MAP, microbiome, or immune system that will later lead to a path forward for UC treatments.
Also, MAP can be a complication of UC. SO if the MAP vaccine proves to be a treatment for CD, it could help some UC patients (see below). But the people saying MAP has been *PROVEN* to be the cause of CD are ignoring some contradictory evidence. Experts do disagree.
"‘Pure’ Ulcerative Colitis (UC) is a different disease to Crohn's, even though many of the symptoms are similar. It is not caused by MAP but is thought to be an auto-immune disease, the trigger for which is still unknown. Crohn’s Disease is caused by MAP infection in a genetically susceptible individual. The latest diagnostic techniques detect MAP in approaching 100% of Crohn's patients. You can, however, get MAP superinfection in someone with UC, making the UC worse. It is also well-known that diagnostic uncertainty is a big problem in Inflammatory Bowel Disease (IBD)... so in someone mistakenly diagnosed with UC when it is actually Crohn's disease, MAP will be the cause. If you have UC, there are 3 ways in which the Vaccine could help:
It is pure UC. Anti-MAP vaccination would protect against secondary MAP infection.
It is UC but superimposed MAP infection is making it worse. Anti-MAP vaccination should improve symptoms.
It looks like UC but it is actually Crohn’s. The vaccine is designed to fix it...and if it works in humans as it does in cattle, it should do so.
The new MAP test currently being developed is a simple, smart test which can be done on blood samples or routine gut biopsies. It is highly accurate and quantitative and will help to dispel this kind of diagnostic uncertainty in IBD."
crohnsmapvaccine.com/faq/