Abstract: Objective To study the impact of surrogate vaccines (SV) on the completion of National Immunization Program vaccine series (NIPVS).Methods A total of 1 428 children aged 2-4 years were selected with lot quality assurance sampling (LQAS) from 34 of 1 004 townships or communities with a population size of ≥ 10 000 residents.Information on immunization of the children was collected to evaluate the coverage of SV and its impact on NIPVS completion.Results Of the 34 townships or communities sampled,24 (70.6%) had provided SV service and of all the children surveyed 1 350 (94.5%) had finished the NIPVS.The NIPVS completion rate was significantly lower among the children in the regions providing SV service but not undertaking the SV (92.1%) than both the rate among those in the regions not providing SV service (96.4%) and among those in the regions providing SV service while not undertaking the SV (97.9%) (χ²=17.00,P<0.01).Unconditional logistic regression analysis indicated that children aged 3-4 years,living in hilly areas,and with fathers having the education of senior high school or technical school were more likely to complete the NIPVS;while those being ethnic minority and those living in regions providing SV service but not undertaking the SV service were less likely to finish the NIPVS.Conclusion Offering SV service exerts either promoting or hindering effect on the completion of NIPVS among children and the children in regions providing SV service should be advised to undertake the SV.