Diphtheria boosters for adults: balancing risks.

Combined tetanus-diphtheria vaccines are now the only means of protecting adults from tetanus or diphtheria. When advising on the benefits and risk of vaccinating for one disease, clinicians now have to consider the other vaccine component, and questions have arisen about where the balance of risk lies for different patients. Five doses of diphtheria-toxoid containing vaccine are probably sufficient protection for individuals who remain in low-incidence countries such as those in most of Western Europe. Adults who remain in the UK are extremely unlikely to be exposed to diphtheria and this needs to be taken into account when assessing the balance of risk where individuals have received fewer than five doses of diphtheria toxoid but five or more doses of tetanus toxoid. In contrast to diphtheria, if someone has received fewer than five doses of tetanus toxoid but is up to date for diphtheria toxoid, the balance of lifelong risk is probably in favour of giving tetanus toxoid irrespective of the individual's diphtheria status. For travellers to diphtheria endemic countries boosters are recommended if more than 10 years has elapsed since the last dose. For individuals who have already received five or more doses of tetanus vaccine in the past, receiving further boosters of tetanus in combination with diphtheria toxoid is unlikely to cause any significant reactions. The only absolute contraindication to such boosters is a previously documented anaphylactic reaction to either diphtheria or tetanus toxoid. Individuals who have a history of such a reaction should be well advised regarding probable risk of infection, symptoms of the disease and the need to seek early treatment.