In this study , 1000 children from 2 months to 6 years of age , eligible for Diphtheria , Tetanus toxoids and whole-cell Pertussis immunization and who referred to 4 health centers , were randomized into 2 groups of regular syringe users ( the Auto-Disable syringe with a 23 gauge and 25 mm needle ) and new syringe users ( the disposable syringe with a 24 gauge and 25 mm needle ) .