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Tuberculosis is caused by infection with tuberculosis bacteria. Only untreated pulmonary tuberculosis is contagious. The usual means of infection is droplet infection from a person who coughs up bacteria. About 10 per cent of those infected become ill, and many years can pass before the disease develops. The disease most often attacks the lungs, but it can also cause infection in other organ systems such as brain membranes, lymph nodes, intestines, bones, joints and kidneys.
Norway is among the countries in the world that have the lowest incidence of tuberculosis, with 300-400 new cases each year. Up until 1997, there was a decline in the number of cases. In recent years, there has been a sharp increase because of increased immigration from countries with a high incidence of the disease. Nearly 90 per cent of those who become ill were born in countries with a high incidence of tuberculosis and most were infected before they came to Norway. Even though the risk of being infected with tuberculosis in Norway is low, it can be higher in situations with a connection to countries where the disease is common. The BCG vaccine is therefore offered to children who have such a connection.
The vaccine contains live, weakened tuberculosis bacteria, Bacille Calmette Guérin, and is called BCG. The vaccine is injected in the upper left arm. Normally a small "pimple" or a weeping sore will appear at the injection site after a couple of weeks. The sore is painless and will heal after a short time. Some people may also get swollen lymph nodes that feel like lumps in the armpit. Up to 80 per cent of those vaccinated are protected against tuberculosis. The protection develops 1–3 months after the vaccination and is long-‐lasting.
It is recommended that the vaccine is given to infants at the age of six weeks. By vaccinating infants, protection is given against the most serious forms of tuberculosis in the first years of life. In the event of there being an infection risk in their surroundings, older children are also offered BCG vaccine. For these children, it may be necessary to perform a test in advance to check if they have already been exposed to infection and would therefore not benefit from the vaccine.
If a child has impaired health or uses medicines, the public health nurse must be informed before vaccination. People with HIV infection and other immune deficiency conditions should normally not have BCG vaccine.
Local reactions that are greater or more prolonged than expected are rare. Swelling in a lymph node near the injection site can occur, which can be unpleasant but is not dangerous. In rare cases, treatment may be needed.
The vaccine used is called the BCG vaccine.