Reactions to the BCG vaccine are uncommon and generally mild.
The most common side effects include fever, headache and swollen glands.
More serious complications, such as abscesses or bone inflammation, are rare.
Most children develop a sore at the injection site. Once healed, the sore may leave a small scar. This is normal and nothing to worry about.
BCG vaccination scar
Virtually everyone when given the BCG vaccination will develop a raised bubble at the site of the injection, which may disappear soon afterwards.
About 2 to 6 weeks after the injection, a small spot may appear at the site of the injection.
It's normal for the spot to turn into a blister, which sometimes oozes before becoming a crusty scab.
It's important to leave the area uncovered as the air will help it to heal. It's normal for it to leave a small scar.
Occasionally, there may be a more severe skin reaction, but this should heal within several weeks.
If you're worried that your or your child's skin reaction is abnormal or that the spot may have become infected, contact a GP.
Allergy to the BCG vaccine
Serious side effects from the BCG vaccine, such as a serious allergic reaction (anaphylactic reaction), are very rare.
All staff who give vaccinations are trained to treat allergic reactions.
Anyone who has an allergic reaction to a vaccine recovers completely with no lasting effects if they're treated promptly.
Page last reviewed: 23 April 2019
Next review due: 23 April 2022