BCG, Bacillus Calmette-Guérin

The BCG, Bacillus Calmette-Guérin vaccine helps prevent Tuberculosis TB. It is given to babies who may be at risk of TB, especially those living in areas with high TB rates or those with parents or grandparents from countries where TB is common.

The BCG vaccine contains a weakened form of the bacteria (germ) that causes TB. Because it is weakened it doesn’t cause TB, but it helps your baby develop protection (immunity) against TB. 

The BCG vaccination is particularly effective in protecting babies and young children against the rarer severe forms of TB such as TB meningitis, swelling of the lining of the brain.

What is TB?

TB is a bacterial infection that usually affects the lungs, but can also affect any part of the body. Infection with the TB germ may not develop into TB disease. TB disease develops slowly in the body, and it takes several months for symptoms to appear.

Most people who have TB infection will never develop TB disease. In these people, the TB germ remains inactive for a lifetime. In other people (for example, those who have weak immune systems), the TB germ may become active and cause TB disease. Most people in this country recover fully after treatment, but this takes several months.

How can you get TB?

You can only catch TB from someone whose lungs or throat are already infected and who is coughing. When they cough, a spray of tiny droplets is produced that contain the bacteria. If someone breathes in the droplets, they too can catch the infection. It takes sharing of an enclosed space with an infected person, for example living in the same house, to be at risk of being infected.

How your baby is immunised

Your baby will be given the BCG vaccination just under the skin, below the deltiod muscle of the left arm. The vaccination is given soon after birth, usually by 28 days after birth.

Side effects

Immediately after the injection, a raised blister will appear. This shows that the injection has been given properly. This blister subsides within a few minutes.

Within two to six weeks of the injection a small spot will appear. This may be quite sore for a few days, but it should gradually heal if you don’t cover it. It may leave a small scar. This is normal.

Occasionally, your baby may develop a shallow sore where they had the injection. If this is weeping fluid and needs to be covered, use a dry non-adhesive dressing – never a plaster – until a scab forms. This sore may take as long as several months to heal.

If you are worried or you think the sore has become infected, contact your local BCG team, GP or 111.

Reasons why your baby shouldn’t have the BCG vaccination

• Your baby has a high fever.
• Rarely, in children who have weakened immune systems, the bacteria in the vaccine can cause serious infection.
• The child is on treatment for cancer or other serious conditions.
• The child’s mother had immunosuppressive biological therapy in pregnancy.
• There is a family history of problems with the immune system (for example HIV, Severe Combined Immunodeficiency (SCID).
• Babies who have or might have SCID (Severe combined immunodeficiency).