Response to two small doses of tetanus toxoid singly or combined as DT or DTP.

DURING the past 20 years we have studied the response to single and multiple antigen preparations in both institutionalized and noninstitutionalized subjects (1-4). In 1943-44, individuals in several of the study institutions were inoculated with different antigrens: diphtheria and tetanus toxoids, typhoid and pertussis vaccines, and scarlet fever toxin, singly or in various combinations. Many of the subjects were still available in 1958 for a followup study to determine their response to a booster injection of some of the antigens. Among the individuals were 19 from an institution for the mentally retarded with a record of no previous injections of tetanus toxoid. These were studied for their response to small doses of tetanus toxoid or an antigen containing tetanus toxoid. They were given two 0.2-ml. intramuscular injections of adsorbed tetanus toxoid, either singly or combined with another antigen, 2 years apart. In 17 of the 19 subjects, the injections were followed by high serum antitoxin titers. Because the results were so favorable, they were made the subject of this report. The material injected and the test methods used were described in an earlier report (5), and pertinent information is given in table 1. The subjects, of both sexes, were residents of the same institution; their ages ranged between 21 and 27 years. The first injection in 7 of the 19 subijects was diphtheria and tetanus toxoids and pertussis vaccine combined (DTP), aluminum phosphate adsorbed; in 7 it was diphtheria and tetanus toxoids (DT), aluminum phosphate adsorbed, and in 5 it was tetanus toxoid, aluminum phosphate adsorbed. In all 19 the second injection, 2 years later, was DT (table 2). The serum antitoxin titers before and after administrationI of the two doses are also shown in table 2, with material injected, sex of the subjects, and age at time of first injection. After the first injection three of the seven subjects who received DTP had tetanus anti-