Hi...., Typhoid vaccine taken by mouth helps prevent typhoid fever, but does not provide 100% protection. Therefore, it is very important to avoid infected persons and food and water that may be infected, even if you have taken the vaccine. To get the best possible protection against typhoid, you should complete the vaccine dosing schedule (all 4 doses of the vaccine) at least 1 week before travel to areas where you may be exposed to typhoid.