What is the ruling on excessively seeking vaccinations and relying upon them, and does that affect a Muslim's belief?

There is no harm in taking vaccines, as they are a permissible means to prevent illness. This does not contradict Islamic creed, as long as one does not believe that the vaccine benefits or harms by itself, but rather believes that benefit and harm come from Allah alone. Sheikh Ibn Baz permitted seeking treatment before the onset of illness to ward off affliction, citing the hadith about dates preventing magic and poison.