Tracking changes in national BCG vaccination policies and practices using the BCG World Atlas.

The BCG vaccine is a widely given vaccine against tuberculosis (TB), yet studies on effectiveness have shown considerable heterogeneity; as a result, BCG vaccine policies vary greatly across the globe and change across geography, and with time and disease burden. The recently updated third BCG World Atlas (www.bcgatlas.org) is a publicly available online database with information on BCG practices across 194 countries. This helpful resource has been used for over 10 years to support clinicians, TB researchers and TB vaccine development worldwide. Here, we summarise main findings from the third BCG Atlas' most recent update which included additional data collected around BCG strain type, vaccine stockouts and associated changes. Longitudinal analysis enables evaluation of changes in TB incidence over time, a method becoming more common in legislation interventions. A large number of countries in the BCG Atlas (156/194 countries) maintain universal neonatal BCG vaccination, of which 51 are considered low TB burden countries. We demonstrate the majority of countries who changed their national policy moved to targeted vaccination for high-risk groups, were in Europe and also had significant decreases in TB incidence both before and after policy change. Globally, the most common BCG strain continues to be the Danish strain, despite its worldwide manufacturing interruption in 2015. Substantial variation and disproportionality exists in which regions were most affected by stockouts between 2009 and 2019. Tracking and understanding the reasoning behind changes to national BCG practices and their impact on TB burden is critical for decision makers as they contemplate how to include BCG vaccination in future immunisation guidelines in low and high TB burden countries.