BCG Vaccine for Tuberculosis: Why Not Universal? Efficacy, Policy, and Alternatives

BCG Vaccination: Global Policy Variation

Bacillus Calmette-Guérin (BCG) is the only licensed TB vaccine. Used in 150+ countries but NOT routine in US, Canada, Netherlands, others.

Reasons for Selective Use

US Policy

• Targeted testing (IGRA preferred) + treatment of latent TB infection (LTBI).
• BCG considered only for: children with high exposure to MDR-TB, healthcare workers in high-risk settings (case-by-case).

Future Vaccines

• M72/AS01E (subunit): 50% efficacy in latently infected adults (Phase 2b).
• VPM1002 (recombinant BCG), MTBVAC (attenuated Mtb) in trials.
• WHO target: new vaccine by 2025-2030.

Current TB Control Pillars

1. Early diagnosis (molecular tests: Xpert MTB/RIF Ultra).
2. Effective treatment (6-mo regimen; shorter for drug-sensitive).
3. Contact investigation + LTBI treatment (3HP, 4R, 1HP).
4. Infection control (ventilation, UVGI, respirators).
5. Address social determinants (poverty, crowding, HIV).

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Factor	Details
Variable Efficacy	0-80% against pulmonary TB (meta-analyses); consistent 70-80% vs meningeal/miliary TB in children. Efficacy ↓ toward equator (environmental mycobacteria interference).
Low TB Incidence	US: <3/100,000. Cost-effectiveness favors targeted testing/treatment over mass vaccination.
Interference with TST/IGRA	BCG → false-positive tuberculin skin test (TST). IGRA (Quantiferon, T-SPOT) not affected but more expensive.
Duration of Protection	10-15 years; wanes. No proven benefit of revaccination.
Contraindications	Immunocompromised (HIV, SCID, chemo), pregnancy, active TB.
Adverse Events	Local ulcer, lymphadenitis (1-10%); disseminated BCG-osis (rare, fatal in SCID).