Mapping Bacillus Calmette-Guérin vaccination coverage in Africa from 1990 to 2022: a novel spatiotemporal modelling study.

BACKGROUND: Bacillus Calmette-Guérin (BCG) protects children from severe tuberculosis and remains the only licensed vaccine for tuberculosis. Subnational estimates of BCG coverage are essential for identifying underserved populations across Africa. This study aimed to map BCG vaccination coverage in Africa from 1990 to 2022.

METHODS: We conducted an advanced Bayesian geostatistical analysis, integrating spatial covariates through stacked ensemble modelling and adjusting for spatial and residual effects to estimate BCG coverage. The analysis included 110 demographic and health surveys, and multiple indicator household surveys, comprising data on 180 449 children from 35 countries in Africa. BCG vaccination coverage among children aged 12-23 months was estimated at a 5 × 5 km spatial resolution. These estimates were then aggregated to second administrative and national levels over the study period weighting by the same age child population. Coverage changes were estimated by comparing coverage metrics in 1990 and 2022. The population-weighted number of unvaccinated children was also estimated at first administrative level. The likelihood of second administrative-level areas achieving the Global Vaccine Action Plan target of 80% coverage threshold in 2020 was quantified using posterior exceedance probabilities.

FINDINGS: Between 1990 and 2022, BCG vaccination coverage increased by at least 25% in 85·32% (95% uncertainty interval 84·11-86·50) of second administrative level areas, with an average increase of 40·52%. Despite this progress, significant geographical disparities remain within and between countries. In 2022, many local areas still had low BCG coverage, including countries with high national BCG vaccination rates. Some countries showed notable improvements, but only a few (such as Burundi, Rwanda, Uganda, Gambia, and Togo) have achieved the Global Vaccine Action Plan target of 80% coverage in all second administrative level areas by 2020.

INTERPRETATION: Despite significant progress in BCG vaccination across Africa over the last three decades, notable geographical disparities persist. These findings suggest a need to prioritise resources and boost BCG coverage, especially in underserved areas.

FUNDING: Curtin University Strategic Scholarship and Australian National Health and Medical Research Council.

TRANSLATIONS: For the Amharic, Icibemba and Swahili translations of the abstract see Supplementary Materials section.