posted the CDC guildeines below.

For patients who have received fewer than three doses or an unknown number of doses of a tetanus toxoid-containing vaccine, tetanus immunization should be administered (table 1) [4]. The preferred vaccine preparation depends upon the age and vaccination history of the patient. For patients with clean minor wounds who have received three or more doses of a tetanus toxoid-containing vaccine, another dose should be given only if the last dose was given 10 or more years ago. For patients with wounds that are more severe than a clean and minor wound (such as, but not limited to, wounds contaminated with dirt, feces, soil, or saliva; puncture wounds; avulsions; wounds resulting from missiles, crushing, burns, or frostbite) who have received three or more doses of a tetanus toxoid-containing vaccine, another dose should be given only if the last dose was given five or more years ago. The vaccine series should be continued through completion as necessary. If there is any doubt about whether or not an adult received the primary series, three doses of Td or Tdap (with Tdap given for at least one of the doses) should be administered; the first dose and second dose should be separated by four weeks and the third dose should be given 6 to 12 months later