Make sure you take out a comprehensive travel insurance policy that covers you for medical expenses. When choosing a policy, check whether the insurance company will make payments directly to providers or reimburse you later for overseas health expenditures.
No specific vaccinations are required for visiting Bosnia.
Tap water is generally drinkable throughout the country.
The Bosnian public health system is divided into ambulanta (first-aid centres), dom zdravlja (community health services) and hospitals. For consultancies and certain clinics there are also private options, though all hospitals are themselves public institutions. The availability of care will depend greatly as to your location and costs vary considerably between doctors.