Adults should get one dose of the tetanus and diphtheria (Td) vaccine every 10 years. For adults who did not get Tdap as a preteen or teen, they should get one dose of Tdap in place of a Td dose to boost protection against whooping cough. However, adults who need protection against whooping cough can get Tdap at any time, regardless of when they last got Td.

Source: CDC