Updated: March 11, 2005
Tuberculosis is caused by the bacterium Mycobacterium tuberculosis. It is generally spread in mucus droplets coughed out by infected people.
Most people with tuberculosis show no symptoms at the time of infection. People who develop symptoms usually do so within one to six months after the start of the infection. Symptoms include fever, night sweats, chills, and cough. Pneumonia, lung collapse, and enlarged lymph nodes may also occur.
The most common form of tuberculosis affects the lungs. Two forms of tuberculosis that become life-threatening are:
More than 25,000 new cases of TB are reported annually in the United States. People who are immunocompromised (have weakened immunity), especially those who are HIV-positive, are at increased risk of developing TB if they are exposed to the disease. Malnourished people as well as those with diabetes or kidney failure are also more likely to develop the disease if exposed.
TB kills more people in the world than does any other infection. Someone in the world is newly infected with TB bacilli every second. Overall, one-third of the world’s population is currently infected with the TB bacillus.
Product: TICE BCG (BCG Live)
Manufacturer: Organon Teknika Corporation
Year Licensed: 1990. This vaccine is thimerosal-free.
Product: Mycobax (BCG Live)
Manufacturer: Aventis Pasteur
Year Licensed: 2000. This vaccine is thimerosal-free.
The TB vaccine is a live, weakened bacterial vaccine made from the bacterium that causes TB in cows. It was first administered to humans in 1921. It has been given to 4 billion people worldwide and has been used routinely since the 1960’s in almost all the countries of the world, primarily in young infants. Changes in the TB bacteria over time have led scientists to create the different TB vaccines used throughout the world, and their effectiveness appears to be highly variable.
The U.S. does not recommend the vaccine for all children because it is not highly effective (see Effectiveness of the Vaccine) and may cause confusion for physicians when trying to interpret a TB skin test. The Netherlands is the only other country that has not recommended this vaccine for all children.
Who should receive the vaccine?
Although TB vaccine is recommended by the World Health Organization and is given in more than 100 countries, in the U.S. it should only be considered in select circumstances. In the U.S., the vaccine should be considered for infants and children who do not test positive for TB but who are:
In addition, vaccination is recommended for health care workers who are employed in settings with patients who have drug-resistant TB, and where comprehensive TB infection-control precautions have been implemented but have not been successful.
Who should not receive the vaccine?
This vaccine is recommended by:
The TB vaccine is given as a shot; one dose is required. Infants may receive the vaccine soon after birth, or later, but preferably before exposure to persons with active tuberculosis.
Studies examining vaccine’s effectiveness against tuberculosis of the lungs have drawn various conclusions; however, one large study found the vaccine to protect about 50% of recipients. Effectiveness rates are highest among those who get the vaccination in early childhood.
Those who receive the vaccine may still develop TB, but approximately 80% of recipients are protected from developing life-threatening forms of the disease, such as miliary disease and meningitis (inflammation of the brain).
Accurate rates of adverse events due to the TB vaccine are difficult to estimate, but serious or long-term complications after TB immunization are uncommon.
Frequent reactions to the TB vaccine include redness, swelling, or soreness at the injection site.
Moderate swelling of the lymph nodes in the armpits or neck, which may progress to pus-filled nodes that require drainage in some people, also occurs. In addition, swelling at the injection site may turn into a pustule and then a scar. An ulcer may develop where the shot was given in some people. These reactions occur after approximately 1% to 2% of immunizations, and may last three months or longer.
Because the TB vaccine is a live vaccine, it may cause TB meningitis, or disseminated TB (TB infection that has spread throughout the body), which occurs at a rate of 0.06 to 1.56 cases per 1 million vaccinated. The vaccine may also cause tuberculosis infection of bone growth centers, which may occur several years after the vaccine was given.
A person previously vaccinated may have a positive reaction to a TB skin test, potentially causing confusion for health care providers attempting to determine if that person has TB.
Outbreaks of drug-resistant strains of tuberculosis, mainly among HIV-infected people, have been reported in the U.S. These tuberculosis cases respond poorly to treatment and have very high death rates.