THE RESULTS of antitoxin titrations of the blood of children who were immunized with protamine diphtheria toxoid1 have previously been published. These data showed that children receiving either one or two doses had somewhat higher and more lasting levels of antitoxin than those reported following the use of equivalent quantities (Lf unit)2 of alum-precipitated toxoid.3 Between eleven and eighteen months after one injection of protamine toxoid (20 to 25 Lf units), 30 per cent of the children had 1/10 unit or more of antitoxin per cubic centimeter of serum. Between nine and fifteen months after two doses, 90 per cent had 1/10 unit or more and 58 per cent had 1/5 unit or more.
Since bleedings were impracticable owing to the objection of the mothers, it was decided to obtain a measure of the duration of the immunity by means of the Schick test. This is admittedly
ROSS V. RESULTS OF SCHICK TESTING THREE YEARS AFTER THE INJECTION OF PROTAMINE DIPHTHERIA TOXOID. Am J Dis Child. 1949;77(4):450–453. doi:10.1001/archpedi.1949.02030040462003