BCG vaccine overview

Overview

The BCG vaccine (Bacillus Calmette-Guérin) is a vaccine that helps protect against tuberculosis (TB), a serious bacterial infection that usually affects the lungs. It is made from a weakened form of bacteria related to TB and is especially important for children in areas where TB is common.

The BCG vaccine is widely used around the world. In many countries, it is part of the routine childhood immunisation programme. In the UK, it is targeted to babies and children at higher risk of TB.

The BCG vaccine is usually given to babies and children up to around 16 years old who are at higher risk of TB. It may also be given to adults who need protection, such as some healthcare workers or people who travel to countries with high TB rates.

Symptoms

Common symptoms

• A small red bump or blister at the injection site that turns into a scab and heals over several weeks.
• Swollen lymph node (gland) under the arm near the injection.
• Mild fever or tiredness for a short time.

Symptoms in children

• The same local reaction (blister and scab) as in adults.
• Occasional mild fever.
• Fussiness or mild discomfort.

Symptoms in older adults

• The BCG vaccine is rarely given to older adults. If given, side effects are similar to those in younger people, such as a local blister and scab.

Causes

Main causes

• The need for the BCG vaccine arises from the desire to prevent tuberculosis (TB) infection, especially in children at higher risk.
• TB is caused by the bacterium Mycobacterium tuberculosis, which spreads through the air when an infected person coughs or sneezes.

Risk factors

• Living in an area with high rates of TB
• Close contact with someone who has TB
• Travel to or from a country with high TB rates
• Having a weakened immune system due to a health condition or medication

When to see a doctor

See a doctor urgently if:

• Signs of a severe allergic reaction after vaccination (see emergency symptoms above).
• A large blister or swelling that spreads rapidly beyond the injection site.

Book a routine appointment if:

• If the injection site does not heal after 4-6 weeks.
• If you develop a severe or worsening rash.
• If you are concerned about any lump or swelling that persists.

Diagnosis

Before giving the BCG vaccine, a healthcare provider may perform a skin test called the Mantoux test to check if you already have immunity to TB or have been exposed. If the test is negative (no reaction), the vaccine can be given.

Tests that may be done

• Mantoux skin test – a small injection of fluid into the skin of the forearm, checked for a reaction after 48-72 hours.
• Blood test for TB (interferon-gamma release assay or IGRA) – sometimes used as an alternative, especially for adults.

What to expect at your appointment

The Mantoux test involves a small injection that may cause mild itching or a small bump. You will need to return to have the result read within a few days. The result helps decide if the vaccine is needed. A positive test means you have likely been exposed to TB and should not have the vaccine. Your healthcare provider will explain what to do next.

Treatment

Side effects of the BCG vaccine are usually mild and do not require medical treatment. The injection site heals on its own over several weeks. If a severe reaction or infection occurs, medical treatment may be needed.

Self-care at home

• Keep the injection site clean and dry. You can bathe as usual, but pat it dry gently.
• Do not apply creams, ointments, or plasters to the blister.
• Let the blister dry naturally and do not burst it.
• If the area is sore, you can take paracetamol or ibuprofen (always follow the recommended dose on the label or ask your pharmacist).

Medical treatments

If the injection site becomes infected, your doctor may prescribe antibiotics. For a particularly large or uncomfortable blister, a healthcare professional may drain it under sterile conditions. In rare cases, if the lymph node is very swollen, it may need to be treated with medication or drained by a specialist.

Living with this condition

After the BCG vaccine, you can continue with normal daily activities. The injection site will go through a normal healing process that can take up to 2-3 months. The site is not contagious and does not need special care beyond keeping it clean.

Lifestyle tips

• Avoid swimming or soaking the injection site for the first few days after the vaccine.
• Wear loose clothing over the injection site to avoid rubbing or irritation.

Diet and exercise

You can eat and exercise as usual. No special diet or activity restrictions are needed after the BCG vaccine.

Mental health and emotional wellbeing

Getting a vaccine can sometimes cause anxiety, especially in children. It may help to explain to your child that the vaccine will protect them from a serious illness. If you have persistent worries about vaccinations, talk to your healthcare provider for reassurance.

Prevention

No vaccine is 100% effective, but the BCG vaccine greatly reduces the risk of severe TB in children. Other measures to prevent TB include avoiding close, prolonged contact with people who have active TB and ensuring good ventilation in rooms.

Vaccines

The BCG vaccine is the main vaccine against tuberculosis. There is currently no other widely used vaccine for TB.

Screening programmes

Screening for TB may be recommended for people who are at higher risk, such as close contacts of someone with TB, or people who work in healthcare. Screening usually involves a chest X-ray and possibly a skin or blood test.

Complications

If left untreated

• If a child does not receive the BCG vaccine and is exposed to TB, they are at higher risk of developing severe forms of TB, such as TB meningitis (infection of the lining of the brain), which can be life-threatening.
• Untreated TB in any age group can cause long-term lung damage and can spread to other parts of the body.
• TB is contagious when it affects the lungs, so it can spread to others, especially in households or close-contact settings.

Long-term outlook

With the BCG vaccine, the risk of severe TB can be greatly reduced, especially for children. The vaccine is safe and effective for most people. Even if you have had the vaccine, it is still important to be aware of TB symptoms (persistent cough, fever, night sweats, weight loss) and seek medical advice if you have been exposed. Early treatment for TB is very effective.

Find support

International organisations

• World Health Organization (WHO)

Local organisations

• NHS UK · United Kingdom

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