BCG Vaccine effetive in Reducing TB Risk in Children especially in Low-Incidence Areas: Meta-Analysis

"The vaccine was associated with an overall 18% reduction in TB infection risk, with greater effectiveness observed in low-burden areas, where it reduced infection rates by 29%," the researchers reported in the International Journal of Infectious Diseases. "However, the protective effect was not significant in high-incidence regions, highlighting the need for context-specific vaccination strategies to enhance TB prevention efforts in these settings."

Chao Song, Department of Pain Medicine, The Affiliated Anning First People's Hospital of Kunming University of Science and Technology, Kunming, China, and colleagues aimed to enhance the understanding of the Bacillus Calmette-Guérin vaccine's effectiveness in preventing tuberculosis infection in children.

For this purpose, the researchers conducted a comprehensive search of PubMed, Web of Science, Cochrane, and Embase databases from their inception up to January 12, 2025. Studies were included if they focused on children under 19 years exposed to pulmonary TB, utilized interferon-gamma release assays (IGRA) for infection assessment, and reported IGRA-positive outcomes for both BCG and non-BCG groups. Pooled estimates were calculated using random-effects meta-analysis, with heterogeneity assessed through the I² statistic.

The study led to the following findings:

• A total of 8,242 participants were enrolled across 32 studies.
• The overall protective effectiveness of the BCG vaccine against TB infection was 18%, with a relative risk (RR) of 0.82.
• In low-TB incidence areas, BCG showed a higher effectiveness of 29%, with a relative risk of 0.71.
• In high-TB incidence areas, the effectiveness was not significant, with a relative risk of 0.95.

According to the authors, BCG vaccination offers protective effectiveness against Mycobacterium tuberculosis infection in children, with a notable 29% reduction in infection risk observed in low TB incidence regions. However, the vaccine did not show significant protection in high-incidence settings, prompting the authors to highlight the need for region-specific vaccination strategies and further research to improve TB prevention where the burden is highest.

The authors also acknowledged several limitations of their study, including the exclusion of immunosuppressed children, reliance on scars or medical records for determining vaccination status, and the inclusion of observational cohort studies, which may introduce selection and misclassification biases. Additionally, high heterogeneity in IGRA results remains a concern. They stress the need for future studies to use more consistent and reliable methods, such as electronic health records, to enhance the accuracy and applicability of findings.

Reference:

Cai, S., Luo, Q., Zhou, G., Guo, X., Dong, Y., Chen, H., Luo, S., He, J., Xia, Y., Li, H., Zhou, Y., & Song, C. (2025). Effect of Bacillus Calmette-Guérin vaccination against Mycobacterium tuberculosis infection in children: An updated systematic review and meta-analysis. International Journal of Infectious Diseases, 107909. https://doi.org/10.1016/j.ijid.2025.107909