@William,
I am professionally very much part of this area of research, and I have been for a long time.
Just for startes, here's a brief list of some (hardly all) major fecal-oral pathogens/diseases, along with which ones have vaccines.
Polio
(great vaccine)
Hepatitis A
(great vaccine)
Shigellosis (bacillary dysentery)
Salmonellosis
Typhoid fever (a specific kind of salmonellosis)
(fairly good vaccine)
Amebiasis, including amoebic dysentery
Cholera
(ineffective vaccine)
E. coli infections incl. enterotoxigenic, enterohemorrhagic, and enteropathogenic
Rotavirus
(new vaccine, seems great)
Norwalk virus
Enteroviruses (of which polio is one)
Ascariasis
Whipworm
And there are other diseases caused by fecal contamination, such as schistosomiasis and hookworm, but the infection is transcutaneous and not oral.
Why do I bring all this up? Because many good people, many organizations, many billions of dollars, many international health initiatives, have been unable to control ANY of these diseases to a reasonable degree in poor countries. The only exception is polio, and the reason is simple -- it's the only one that is part of a long vaccine campaign. Fortunately, polio is one of the worst of these illnesses.
I trained in infectious diseases at Harvard, and there is a major cholera research institute there (based at Massachussets General Hospital). Some of them work on cholera vaccines. I asked once why they need a vaccine as opposed to just using public health measures like hygiene and sanitation, and the answer is in the results -- it just hasn't worked. In Bangladesh there are frequent floods that disrupt their considerable efforts at sanitation, and cholera epidemics are frequent. In Zimbabwe the country's infrastructure has collapsed in the last decade and now they're facing cholera again. Vaccines may be the best intervention to interrupt transmission.
The same is true for rotavirus, which kills more children than any other single infectious agent. The new rotavirus vaccine, introduced in the US(!) within the last few years, has cut down rotavirus admissions by around 70-80% -- and we have
good hygiene here. Imagine how hard it is in developing countries.
That's not to say that vaccines are the only answer, and EVERYONE in tropical medicine and global health knows that a tremendous amount of good could be done with simple things like hygiene, sanitation, nutrition, prenatal care, and ALSO childhood vaccines. But honestly effective hygiene and sanitation are a lot more difficult than it sounds, and it requires a tremendous amount of financial investment in otherwise unstable, impoverished places.