The protective titre of antitoxin to diphtheria following vaccination is: (A) 0.01 IU/ml, (B) 0.05 IU/ml, (C) 0.1 IU/ml, (D) 0.5 IU/ml
Answer is A. Active immunization by vaccination with diphtheria toxoid is the key in preventing diphtheria. . Serum antitoxin concentration of 0.01 IU/mL is usually accepted as the minimum protective level. 0.01 IU/mL is considered to provide basic protection and 0.1 IU/ml is considered to provide complete or total protection.