All travellers should be vaccinated according to national recommendations. Vaccination against diphtheria is usually given as triple vaccine – DTP or DTaP (diphtheria/tetanus/pertussis or diphtheria/tetanus/acellular pertussis). After the initial course of three doses, additional doses may be given as DT until 7 years of age, after which a vaccine with reduced diphtheria content (Td) is given. Since both tetanus toxoid (see below) and diphtheria toxoid can reasonably be given on a booster basis about every 10 years, there is no reason to use monovalent diphtheria vaccine. In some countries, adult boosters that contain acellular pertussis (TdaP) are being introduced.