• Implementing any vial-opening threshold policy for measles-containing vaccine can have numerous system-wide effects. The vial opening threshold policy that maximizes vaccine availability and cost savings varies from country to country. • According to the modeling, cold chain restraints played a major role in mediating the effects of different vial opening thresholds. When no cold chain constraints exist, the most beneficial policy is to open a vial for any number of children. • In Benin and Mozambique, which had median session sizes of two to six, the 30% vial opening thresholds were the most beneficial. In Niger, where the median session size is nine, the 60% threshold performed well. • In Benin, switching to 5-dose vials and using either no threshold or 30% threshold led to improvement in MCV availability of 10% compared to using 10-dose MCV with no threshold.