When an injured patient visits the ED, unnecessary injection of tetanus immunoglobulin (TIG) may cause side effects and also increase the medical expense.5 Further, the opportunity of assessing a rising tetanus antibody titer may be missed after simultaneous injection of tetanus-diphtheria vaccine (Td) and TIG. According to age, the elevation of the tetanus antibody titer after tetanus prophylaxis might be not equivalent because of different levels of basal immunity and the time-interval of the last tetanus vaccination. Therefore, we wanted to determine whether TIG influences the formation of tetanus antibody after simultaneous tetanus vaccination according to age and the time-interval of the last tetanus vaccination.