Hello dear, If 3 primary and 3 booster doses ( at 18 months, 5 years and 10 years) are taken ( as done in routine to all children), repeat dose is required only after 10 years. Exceptions are major injury, surgery when repeat dose is required. Do not go for Tetanus shot for every minor injury, as many people do as overuse may cause side effect ( immune-complex mediated reactions). Hope this might be helpful to you.