What vaccinations and medicines are required for travel to Eastern Europe?
"Eastern Europe" is kind of a broad term, and depending on definition may consist of quite different countries.
In any case, Grzenio is right in that the recommended vaccinations are pretty much the same as for Western Europe (or North America). (MastaBaba is also right that these are recommendations, not requirements.) To be more specific:
Vaccines recommended for all
Vaccines also to be considered, based on a personal risk estimate
Depending where you want to travel to you could check out the CDC destination page, which gives you a list of countries and possibly required vaccinations.
Though it may be more beneficial to give an indication of where exactly you're going to get a more definitive or streamed down list.