STUDIES ON THE ADEQUATE COMPOSITION OF DIPHTHERIA AND TETANUS TOXOIDS^|^mdash;WITH REFERENCE TO THE AMOUNTS OF TOXOIDS AND ALUMINUM ADJUVANT

Immune response of man to tetanus and diphtheria-tetanus combined toxoids with different compositions was investigated, with special reference to the long-term immunity. Adsorbed tetanus toxoid with a potency of about 25 IU per human dose endowed a long-lasting immunity sufficient to prevent tetanus to the vaccines of various age groups, when administered in two doses, followed by a booster injection. Two doses of adsorbed diphtheria-tetanus combined toxoid with potencies of about 20 IU per dose for both components were sufficient to give immunity in infants against diphtheria and tetanus. However, a booster injection should be given within a year to endow a long-lasting immunity. In the case of booster immunization of children with a complete history of immunization against diphtheria and tetanus, a potent long-term immunity was endowed by a single injection of diphtheria-tetanus combined toxoid (plain) with 1 and 3.5 IU per dose, for diphtheria and tetanus components, respectively.