Pharmacology · Bacterial and antimalarial vaccines
BCG vaccine (bacille Calmette-Guérin) !
Live attenuated tuberculosis vaccine. It protects children from severe forms, such as tuberculous meningitis and miliary tuberculosis.
Updated 2026-11-01
Also called: Bacille Calmette-Guérin, Tuberculosis vaccine
Mechanism of action
It contains a live attenuated strain of Mycobacterium bovis. Limited replication in the skin induces cell-mediated immunity (T cells and activated macrophages) that limits spread of tuberculosis. It prevents deaths and severe forms in childhood; its protection against adult pulmonary tuberculosis is variable.
- Live attenuated bacteria are placed in the skin
- They activate T cells and macrophages against mycobacterial antigens
- Cell-mediated immunity contains bloodstream spread
- Protects mainly against TB meningitis and miliary TB in children
Pharmacokinetics
- Absorption
- Single intradermal dose, often near birth; the bacteria replicate to a limited extent in the skin
- Onset and duration
- Cell-mediated immunity develops over the following weeks
Indications
- Prevention of severe tuberculosis in children in countries with a high burden of the disease Tuberculosis →
Adverse effects
Common
- Local inflammatory reaction at the intradermal site
Contraindications
- Immunosuppression, including HIV infection
- Pregnancy
Key interactions
- Tuberculin skin test
- BCG can cause a false-positive tuberculin skin test; interferon-gamma release assays (IGRA) are not affected
What is monitored
- Immune status and maternal HIV exposure before giving
- Course of the local reaction
Administration and safety
- Strictly intradermal
- Live vaccine: keep in the cold chain as the leaflet states
- Not given to immunosuppressed people
Nursing care
- Confirm there is no immunosuppression (including the newborn's HIV exposure)
- Record the vaccine and batch on the vaccination card
- Explain to the family why a future tuberculin skin test may be positive
Pregnancy and breastfeeding
Contraindicated in pregnancy because it is a live vaccine.
Test yourself
Think of the answer, then tap the question to see it.
What does BCG protect against best?
Severe forms of tuberculosis in children, such as tuberculous meningitis and miliary tuberculosis; its pulmonary protection in adults is variable.
Why is BCG contraindicated in people with HIV?
It is a live vaccine: in an immunosuppressed person the attenuated bacterium can disseminate.
Which diagnostic test is preferred in a BCG-vaccinated person, and why?
IGRA (a blood test), because BCG can make the tuberculin skin test positive but does not affect IGRA.
Related conditions
← Back to the class: Bacterial and antimalarial vaccines
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Bacille Calmette-Guérin (BCG) Vaccine for Tuberculosis (Centers for Disease Control and Prevention, 2025); Tuberculosis (World Health Organization, 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 40 (McGraw Hill, 2023); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.