The use and results of diphtheria immunization.

After a brief historical review of the events leading to the development of diphtheria prophylactics, the author discusses the effect of immunization on diphtheria epidemiology and the principles governing the choice of prophylactics. For immunization campaigns to be really effective a high proportion of the population must be immunized, and the pre-school age-groups must be included. Indeed, there is evidence that primary immunization should not be delayed beyond the third or fourth month of life. The prophylactic used should be antigenically highly potent and should confer long-lasting immunity with three injections at the most.The author then considers the use of combined immunization, which is approached with caution in some countries but is generally accepted in North America, and goes on to discuss the immunization of adults. The fact that adults may have severe reactions to parenterally administered diphtheria toxoid has led to attempts to develop reaction-free prophylactics. Toxoid administered orally appears not to cause reactions but is not yet so effective as parenteral toxoid.