IMMUNITY TO TETANUS INDUCED BY A THIRD DOSE OF TOXOID TWO YEARS AFTER BASIC IMMUNIZATION

In my previous study1on the appearance of tetanus antitoxin in the blood serum following two injections of 0.5 cc. each of combined alum-precipitated diphtheria and tetanus toxoids, special reference was made to the influence of the interval between injections. It was also shown that 94.6 per cent of a group of 186 allergic children attained a protective level of tetanus antitoxin, the critical level being placed at 0.01 American unit of antitoxin per cubic centimeter of blood. In a subsequent study2a third, or "booster," injection of 0.5 cc. of the combined alum-precipitated toxoids was given to 65 of the 186 children used in the first report. Nine of these 65 children had failed to attain adequate immunity after two doses of the combined alum-precipitated toxoids. The "booster" dose was administered from three to fifteen months after the completion of primary immunization with two doses of combined