COMPARISON OF THE SAFETY AND IMMUNOGENICITY OF THE LYOPHILIZED MERIEUX SEED AND THE WORLD-HEALTH-ORGANIZATION WORKING REFERENCE BCG VACCINES IN SCHOOL-AGED CHILDREN IN SENEGAL

In order to validate two new lots of Merieux BCG vaccine (Merieux seed derived from strain 1072), a calibration study was performed to compa re their safety and immunogenicity to a full dose of the WHO-reference BCG vaccine (Tokyo strain 172) as well as the WHO-reference vaccine g iven at 1/10 of its normal concentration, in an open, randomized, four -arm, multicenter study in Senegal. A total of 1041 healthy Senegalese children aged 8-10 years were screened for participation in this stud y, of whom 548 had a negative Mantoux test and complied with inclusion and exclusion criteria. These children were randomly allocated a sing le dose of one of the following vaccines: full-dose Merieux BCG vaccin e (lot E0650); full-dose Merieux BCG vaccine (lot E0624); full-dose WH O-reference vaccine (Tokyo strain 172); or 1/10 dose WHO-reference vac cine. A follow-up examination, including a tuberculin test, was perfor med 10-12 weeks after BCG vaccination for 465 (85%) children: 236 Meri eux BCG vaccine (117 lot E0650; 119 lot E0624); 115 full-dose WHO; 114 1/10 dose WHO. The percentage of subjects with a positive tuberculin test after Vaccination was significantly lower (p < 0.001) in the 1/10 dose group (81.5%) compared to the other three groups (> 96%). The me an induration diameter was significantly smaller in subjects who recei ved the low-dose of WHO vaccine compared to the others, according to a nalyses considering all subjects vaccinated, as well as only those sub jects with a positive tuberculin test after vaccination. More children in the low-dose group did not have a vaccination scar, and the mean d iameter of scars was smaller in this group. The rate of tuberculin rea ctions, the classification of reactions (Palmer and Edwards), and the characteristics of the vaccinal lesion were similar for the Merieux BC G vaccines and the full-dose WHO-reference vaccine. All vaccines were safe, as evidenced by the absence of adenitis or suppurative adenitis during the course of the study. Results from this trial show that the two lots of Merieux BCG vaccine behave equally as well as the full-dos e WHO-reference BCG vaccine. The WHO-reference vaccine, given at 1/10 of its normal concentration was significantly less immunogenic, accord ing to ail parameters evaluated. (C) 1998 Elsevier Science Ltd. All ri ghts reserved.