No vaccine is required to go to Turkey. However, make sure that your DTP vaccines (diphtheria, tetanus, polio) are à jour. Il est also recommended that you get vaccinated against influenza during transmission periods. We can never repeat it enough: tap water is not drinkable in Istanbul! There is no need to play the hero or globetrotter who has seen and experienced everything, the Turks themselves do not drink it, even if it is boiled...