The use of mixed diphtheria-pertussis-tetanus antigens.
The author reviews the use of mixed diphtheria-pertussis-tetanus antigens in the light of the information which has become available in recent years. When diphtheria toxoid and tetanus toxoid, adsorbed or unadsorbed, are added to either plain or adsorbed pertussis vaccine, a satisfactory level of diphtheria antitoxin can be obtained in children over 6 months of age and of tetanus antitoxin in children of any age. As to the duration of immunity, it appears that provided three doses of mixed antigens are given for the primary immunization of children 6 months old a substantial proportion will have effective antitoxin titres three years later, but that with two doses only the antitoxin levels fall more rapidly.Reviewing the evidence, the author considers that mixed antigens will be useful in future immunization campaigns, although he makes it clear that extensive investigations, particularly on the immunizing effect of the pertussis component, must be undertaken before their value can be finally assessed.The reactions to and complications after inoculation with mixed antigens are then discussed, particularly in relation to convulsions, encephalopathy, and poliomyelitis. Finally, the author considers provisional recommendations for the use of mixed antigens, pointing out that the main question in all countries is whether the advantages of giving all three antigens simultaneously to children under 6 month of age, necessary because of the pertussis mortality in the first months of life, outweigh the disadvantages.