“…Most Schick negative individuals show the tuberculin-type of reactivity to purified toxoid, and in these per sons reactions cannot be avoided. Since these individuals already possess a level of antitoxin however, very small "booster" doses may be employed, reliance being placed upon the repeatedly demonstrated (112,113,117) effectiveness of small doses of diph theria toxin in inducing pronounced anamnestic responses. The Schick test dose may itself serve as an adequate booster stimulus.…”