How the Vaccine Works
The BCG vaccine is a live, attenuated vaccine, meaning that it infects the individual but does not give them any disease (unless the person is immunocompromised, they can then contract a systemic BCG infection). The BCG vaccine contains weakened forms of the organism M.tuberculosis
through attenuation. The attenuated form of M.tuberculosis
is obtained by serial passage or culture of the active organism in culture media or cells. The vaccine is based on the concept of “cross reacting antigens” where the killed Mycobacterium
strain is used to stimulate the immune system into mounting an attack on M.leprae
Potential Side Effects
The BCG vaccine may cause redness and mild swelling where the injection was given. However, these symptoms should improve over time. Other minor side effects include red bumps at the injection site, loss of appetite, muscle or joint pain, low grade fever 1-2 days after vaccination, or enlarged lymph node. Serious side effects are rare, but may include signs of allergic reaction such as difficulty breathing, wheezing, chest tightness, severe rash, or hives, fever of 103 degrees F or higher, and skin ulcer at the injection site. BCG vaccination may cause a positive reaction to the tuberculin skin test (TST) which may complicate decisions about prescribing treatment.