The BCG vaccine

The Bacillus Calmette-Guerin (BCG) vaccine protects against tuberculosis (TB), an infection spread by bacteria (mycobacterium tuberculosis). TB usually affects the lungs, and is spread by coughing and sneezing, but it can also involve other organs and joints in the body and sometimes causes meningitis (swelling of the membranes surrounding the brain and spinal cord).

BCG vaccines contain live attenuated bacteria (bacteria that have been weakened in the laboratory so that they can't cause disease) and only one company (Statens Serum Institut) is currently licenced to produce BCG vaccine in the EU. Unlike the other childhood vaccinations that are given by a doctor or nurse at your local GP surgery, BCG is usually administered to babies shortly after birth, in the maternity hospital or an HSE clinic.

Before the BCG vaccine was available, it is estimated that a quarter of all deaths in the 19th century were caused by TB (then commonly called consumption). TB still causes 2 million deaths every year, but is rare in developed countries with routine BCG vaccination.

The bacterium that causes TB was discovered in 1882 by Robert Koch and the BCG vaccine was named after Calmette and Guerin who developed the vaccine in France in the early 1900s. TB can be hard to treat - early success with antibiotics has now led to strains of bacteria that are resistant to these drugs, so vaccination is the only effective way to protect people against the disease.

Most common side effects are mild and temporary. They are a result of the child's immune system responding to the vaccination, and making antibodies that will protect the child in the future. Most side effects will ease after a day or two and any discomfort can be treated with over-the-counter medicines such as paracetamol or ibuprofen (ask your pharmacist for medicine appropriate for your child's age).

Before getting the vaccination, speak to your doctor if your child has been sick or 'off form' over the past few days. Illness can reduce the effectiveness of a vaccine. The nurse or doctor administering the vaccine will check your child's temperature first, to see if they may have any other infections or illnesses.

Common side effects of the BCG vaccine that are usually no cause for concern: slight swelling, redness and tenderness at the injection site, a small lesion that becomes an ulcer after a few weeks. The ulcer can take a few months to heal and will usually leave a small, flat scar. Some babies have a slight and temporary swelling of lymph nodes in the armpit.

Other rarer side effects of the BCG vaccine include a fever, larger swellings in the armpits (bigger than 1cm), an oozing ulcer at the injection site, and headache. These side effects are rare and have been reported in very few children.

Remember that the benefits of receiving vaccines that protect your child from serious diseases hugely outweigh any mild side effects from vaccination.

If you are concerned about your child, contact your doctor or local hospital for advice.

Allergies to substances within vaccines can occur, though they are very rare (they happen in fewer than 1 in 10,000 people receiving the vaccine). An allergic reaction to a vaccine would happen quickly - probably before you left the GP's surgery. Signs of an allergic reaction may include itchy skin, rash, shortness of breath and swelling of the face or tongue.

Before getting the vaccination, speak to your doctor if your child has experienced any allergic reactions previously.

If you are concerned about your child, contact your doctor or local hospital for advice.

Vaccines are tested exhaustively before they are provided to the public (it normally takes 10-15 years to develop a new vaccine). BCG (the TB vaccine produced by Statens Serum Institut) was licenced for use in the USA in 1995. Clinical trials were carried out initially on over 5,000 children (clinical trials are used to assess the safety of the vaccine and to collect data on possible side effects, such as those listed above), and the vaccine is now used routinely in many countries.