<s>[INST] My daughter aged 3.5 yrs old had fever for three days and got controlled after giving medicine. again on 5th day she had fever so doctor advised to take Blood test and the resulted as S.Thipho O is positive. Six months before my daughter was affected by Typhoid fever and got cured and even she was given Typhoid prevention injection. i want to know why this fever again affect my daughter even the prevention injection given. kindly advice me. Thanks [/INST] Efficacy of commonly used typhoid vaccines for prevention of typhoid is nearly 50-70 percent. Recurrence means she got infection from some source /carrier (typhoid is water /foodborne disease). Although not 100 % effective, vaccine does prevent against severe form of disease, commonly used vaccines are to be repeated every 3 yrs. If there is recurrence in family, someone may be a carrier in family, like person who is preparing food, that also need to be vaccinated. </s>