[The determination of the protective potency of the diphtheria component in combined vaccines by the indirect hemagglutination (IHA) method].

The sheep erythrocytes which were coated with diphtheria toxoid by formaldehyde-tannic acid method are used to identify the specific antibody response in guinea-pigs that were immunized by adsorbed DPT and DT. It has been demonstrated that this antibody response detected by IHA is highly correlative with protective antibody response detected by Lethal Challenge Test. It has also been determined by IHA method that the immunization potency of diphtheria component can be detected by testing only one immunized guinea-pig.