BCG (TB) vaccine side effects

Virtually everyone who has a BCG vaccination will develop a raised blister at the site of the injection immediately afterwards. This is normal and is nothing to worry about.

BCG injection scar

Two to six weeks after the injection, a small spot may appear at the site of the injection. It can grow into a circle up to 7mm in diameter and may become crusty where fluid has dried on the surface. It can be painful and bruised for a few days, but will eventually heal. It usually leaves a small scar.

Rarely, some people may have a more severe skin reaction. This should heal within a few weeks.

If you are worried that you or your child's skin reaction is abnormal or that the spot may have become infected, contact your GP.

Allergy to the BCG vaccine

Serious side effects, such as an anaphylactic reaction (a serious allergic reaction), are very rare. They occur in less than one in a million cases. All staff who give vaccinations are trained to treat allergic reactions. And those who have an allergic reaction to a vaccine  recover with no lasting effects with treatment.

To find out more, read Vaccine safety and side effects.

Monitoring safety of the BCG vaccine

In the UK, the safety of vaccines is monitored through the Yellow Card Scheme by the Medicines and Healthcare Products Regulatory Agency (MHRA) and the Commission on Human Medicines.

Most reactions reported through the Yellow Card Scheme have been minor, such as redness and swelling at the injection site, rashes, fever and vomiting.

Find out How to report a vaccine side effect.

Last Updated: 17/02/2022 16:01:01
The information on this page has been adapted by NHS Wales from original content supplied by NHS website nhs.uk