<prompt> The protective titre of antitoxin to diphtheria following vaccination is0.01 IUml0.05 IUml0.1 IUml0.5 IUml  <response>: Active immunization by vaccination with diphtheria toxoid is the key in preventing diphtheria. . Serum antitoxin concentration of 0.01 IUmL is usually accepted as the minimum protective level. 0.01 IUmL is considered to provide basic protection and 0.1 IUml is considered to provide complete or total protection. 