Efficacy, immunogenicity, and safety of BCG revaccination against Mycobacterium tuberculosis: A systematic review and meta-analysis.
Syed Hassan Ali, Shanza Shakir, Umais Ahmed Shaikh et al.
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In 30 seconds
This systematic review and meta-analysis assessed the efficacy, immunogenicity, and safety of BCG revaccination against tuberculosis. Six randomised controlled trials involving 2400 participants were included. Revaccination did not significantly affect initial or sustained QFT conversion (RR 0.99 and RR 0.80, respectively), despite moderate increases in CD8+ T-cell and cytokine-producing CD4+ T-cell responses. Adverse events increased, while upper respiratory tract infections were less frequent (RR 0.37). The findings indicate that measurable immune activation did not translate into clear protection against Mycobacterium tuberculosis.
Key findings
- Across six RCTs and 2400 participants, BCG revaccination had no significant effect on initial QFT conversion (RR 0.99) or sustained conversion (RR 0.80).
- Revaccination moderately increased CD8+ T-cell responses (p = .01) and cytokine-producing CD4+ T-cell responses (p = .008).
- Adverse events increased, although upper respiratory tract infections were less frequent (RR 0.37).
Why it matters
The results underscore that immune-response measures alone may not establish clinically meaningful protection against tuberculosis. For vaccine evaluation, immunogenicity should be interpreted alongside outcomes that quantify protection and safety, particularly in high-risk populations.
What to keep in mind
The review included six RCTs; the abstract does not provide further detail on trial populations, follow-up, or the nature and magnitude of adverse events.