BCG vaccine: durable protection against TB for up to 20 years

Takeaway

• Bacillus Calmette-Guérin (BCG) vaccination appears to prevent Mycobacterium tuberculosis (TB) acquisition in adult contacts and limits progression to latent tuberculosis infection (LTBI).

Why this matters

• Consider BCG vaccine history and time since vaccination in at-risk adults presenting post-TB exposure to facilitate best management strategies. 
• Ensure familiarity with ECDC BCG vaccine scheduler.

Key results

• 3453 participants, 3399 included in complete-case analysis, median age 32 (interquartile range, 25-43) years.
• LTBI prevalence:
  • 27.5% (951) overall;
  • 27.0% (809) among vaccinated vs 31.4% (142) among unvaccinated;
  • OR, 0.81 (P=.054).
• Multivariate, BCG-LTBI association:
  • OR, 0.70 (P=.0017).
  • Vaccine effectiveness (VE): 30% (95% CI, 13%-44%).
• BCG protection (ORs, 95% CIs) with vaccination at age <2 years for adults vaccinated:
  • 11-20 years ago: 0.55 (0.33-0.90); 
  • >20 years ago: 0.78 (0.60-1.00).
• BCG protection (ORs; 95% CIs) with vaccination at age >2 years for adults vaccinated:
  • ≤10 years ago: 0.31 (0.15-0.63); 
  • 11-20 years ago: 0.73 (0.48-1.10); and
  • >20 years ago: 0.67 (0.46-0.98).

Study design

• Cross-sectional analysis assessing BCG VE durability against LTBI in at-risk, UK adults.
• Funding: National Institute for Health Research.

Limitations

• Observational. 
• Measurement errors, misclassifications.
• Self-report bias.
• Residual confounding.
• Interferon-gamma release assay (IGRA) specificity.