What is the best way to explain the BCG (Bacillus Calmette-Guerin) vaccine to a patient?

How to Explain BCG Vaccine to a Patient

BCG is a live, weakened tuberculosis vaccine given through multiple small skin punctures on the upper arm that helps protect against severe forms of TB, especially in children, though it is rarely used in the United States because we have better ways to prevent TB through testing and treatment. 1, 2

What BCG Is and How It Works

• BCG stands for Bacillus Calmette-Guérin, which is a weakened form of bacteria related to the one that causes tuberculosis. 3
• The vaccine contains live but attenuated (weakened) bacteria that cannot cause tuberculosis disease but can train your immune system to fight TB. 3
• It is the only licensed tuberculosis vaccine in the world and has been used for 100 years, though its effectiveness varies from 0-80% depending on the population. 4, 5
• BCG provides excellent protection (>80%) against the most serious forms of TB in children, including TB meningitis and disseminated TB, but protection against lung TB in adults is much more variable. 2

How the Vaccine Is Given

• The vaccine is applied to the skin of your upper arm (deltoid area) using a special device with 36 small points that puncture the skin. 3
• The procedure involves placing drops of vaccine on your cleaned skin, then pressing a multiple-puncture device firmly into the skin for 5 seconds. 3
• This is NOT given as a regular shot - it is not injected into the muscle, under the skin, or into a vein. 3
• The vaccination site should be loosely covered and kept dry for 24 hours after vaccination. 3

What to Expect After Vaccination

Normal Reactions:

• Within 2-3 weeks, a small bluish-red bump (pustule) will form at the vaccination site. 6, 1
• After about 6 weeks, this pustule will open and form a small draining sore about 5mm (1/5 inch) in diameter. 6
• The sore should be kept clean and bandaged while it drains. 6, 1
• The site will scab over and heal within 3 months, usually leaving a permanent small scar. 6, 1
• You may experience flu-like symptoms for 24-48 hours after vaccination. 3

Potential Scarring:

• Most people (28-33%) develop slightly raised (hypertrophic) scars at the vaccination site. 6
• About 2-4% of people develop larger, raised keloid scars. 6

Important Follow-Up

• You will need a tuberculin skin test 2-3 months after vaccination to document your immune response. 6, 1, 3
• The results in millimeters will be recorded in your medical record. 6, 1
• After BCG vaccination, future TB skin tests may be positive even if you don't have TB infection, which can make diagnosis more complicated. 6, 2

Who Should NOT Receive BCG

Absolute Contraindications:

• Anyone with a weakened immune system, including HIV infection, cancer (leukemia, lymphoma), or congenital immunodeficiency. 6, 1
• People taking immunosuppressive medications (steroids, chemotherapy drugs, or radiation therapy). 6
• Pregnant women, though no harm to the fetus has been documented. 6, 1
• Anyone who already has a positive TB skin test (≥5mm induration). 6, 3

Why BCG Is Rarely Used in the United States

• BCG vaccination is rarely indicated in the United States because we have effective TB control through early case detection, treatment, and preventive therapy with medications like isoniazid. 6, 2
• The vaccine's variable effectiveness, especially in adults, combined with interference with TB skin testing, makes it less useful than other prevention strategies. 6

Limited Situations Where BCG Might Be Considered:

• Children who cannot be separated from an adult with untreated, infectious TB and cannot take preventive medication long-term. 6, 2
• Children continuously exposed to TB strains resistant to both isoniazid and rifampin (the main TB medications). 6, 2
• Healthcare workers in very specific high-risk settings where most TB cases are resistant to standard medications, though this is evaluated on an individual basis. 2

Important Safety Information

• The vaccine contains live organisms - though they won't survive long in a dry state, infection of others is theoretically possible, so basic hygiene is important. 3
• Contact your doctor immediately if you develop fever of 103°F or higher, or if local reactions persist longer than 2-3 days. 3
• All equipment used for BCG must be handled as biohazardous material. 3

Key Takeaway for Decision-Making

Before receiving BCG, your doctor should discuss with your local TB control program whether this vaccine is truly necessary for your situation, as there are usually better alternatives available in the United States, including preventive medication therapy that is 61-83% effective in preventing active TB disease. 6