OBJECTIVE: BCG vaccination is frequently delayed in low-income countries. Restrictive vial-opening policies, where a vial of BCG vaccine is not opened for few children, are a major reason for delay. During delays, children are unprotected against tuberculosis (TB) and deprived of non-specific effects of BCG. We assessed the potential effect and cost-effectiveness of disregarding the restrictive vial-opening policy, on TB and all-cause mortality, in children aged 0-4 years in Guinea-Bissau. METHODS: Using static mathematical models, we estimated the absolute and percentage change in TB and all-cause deaths, in children aged 0-4 years, between the current BCG vaccine restrictive-opening policy scenario, and a non-restrictive policy scenario where all children were vaccinated in the first health-facility contact. Incremental cost-effectiveness was estimated by integration of vaccine and treatment costs. FINDINGS: Disregarding the restrictive BCG vial-opening policy was estimated to reduce TB deaths by 11.0% (95% uncertainty range (UR):0.5%-28.8%), corresponding to 4 (UR:0-15) TB deaths averted per birth cohort in Guinea-Bissau, resulting in incremental cost-effectiveness of US$ 911 per discounted life-year gained (LYG) (UR:145-9142). For all-cause deaths, the estimated reduction was 8.1% (UR: 3.3%-12.7%) corresponding to 392 (UR:158-624) fewer all-cause deaths and an incremental cost-effectiveness of US$ 9 (UR:5-23) per discounted LYG. CONCLUSIONS: Disregarding the restrictive BCG vial-opening policy was associated with reductions in TB deaths and all-cause deaths and low cost-effectiveness ratios. Our results suggest that it would be cost-effective to disregard the restrictive vial-opening policy. Other settings with similar practice are also likely to gain from disregarding this policy.