Although no specific vaccinations are required for traveling to Tibet or Bhutan, it is always to consult your doctor beforehand. Some of the vaccines that are advised to all travelers are Hepatitis A, Typhoid, and Hepatitis B among others. You can also visit the given links to have more info at http://www.cdc.gov/flu/avianflu/ or http://wwwnc.cdc.gov/travel/page/vaccinations.htm