Figure 1.

A decision tree model for cost-effectiveness analysis of three polio immunization schedules. The decision tree model had the following hypotheses: (1) 100% coverage of polio immunization in the study population; (2) no self-paid polio-containing vaccines in the study population; (3) no occurrence of VAPP after four-IPV immunization in the study population; (4) cost of cold-chain services, human resources, and administration remain identical across three polio immunization schedules. IPV, inactivated polio vaccine; VAPP, vaccine-associated paralytic poliomyelitis.