This study is a randomized, blinded, active-controlled phase I clinical trial to evaluate the safety and preliminary immunogenicity of the Diphtheria-Tetanus-acellular Pertussis Component Combined Vaccine (DTacP) in subjects (aged 2 months to 6 years). Primary safety endpoints are the occurrence of solicited adverse events within 30 minutes after each dose, the occurrence of solicited adverse events within 7 days after each dose, the occurrence of unsolicited adverse events within 30 days after each dose, and the occurrence of adverse events 30 days after immunization. The secondary safety endpoint is the occurrence of serious adverse events (SAEs) within 12 months after immunization. Secondary immunogenicity endpoints are the geometric mean concentration (GMC), geometric mean fold increase (GMFI), seropositive rates, seroconversion rates, or 4-fold increase rates of anti-DT, anti-TT, anti-PT, anti-FHA, and anti-PRN antibodies 30 days after immunization. The exploratory endpoints are the GMC, GMFI, seropositive rates, seroconversion rates, or 4-fold increase rates of anti-DT, anti-PT, and anti-FHA neutralizing antibodies 30 days after immunization in all groups, the GMC and seropositive rates of anti-DT, anti-TT, anti-PT, anti-FHA, and anti-PRN antibodies 12 months after primary immunization in the infant group, the seropositive rates and geometric mean tie (GMT) of anti- type I, type II, type III poliovirus neutralizing antibodies 30 days after immunization in all groups, the seropositive rates and geometric mean tie (GMT) of anti- type I, type II, type III poliovirus neutralizing antibodies 12 months after primary immunization in the infant group.