Vaccinations are not required, and Italy doesn't present any more health worries than anywhere else in Europe; the worst that's likely to happen to you is suffering from the extreme heat in summer or from an upset stomach (shellfish is the usual culprit). The water is perfectly safe to drink and you'll find public fountains (usually button- or tap-operated) in squares and city streets everywhere, though look out for acqua non potabile signs, indicating that the water is unsafe to drink. It's worth taking insect repellent, as even inland towns, most notoriously Milan, suffer from a persistent mosquito problem, especially in summer.