BCG vaccine screened for active tuberculosis. BCG is also contraindicated in certain people who have IL-12 receptor pathway defects. BCG is given as a single intradermal injection at the insertion of the deltoid. If BCG is accidentally given subcutaneously, then a local abscess may form (a "BCG-oma") that can sometimes ulcerate, and may require treatment with antibiotics immediately, otherwise without treatment it could spread the infection causing severe damage to vital organs. However, it is important to note an abscess is not always associated with incorrect administration, and it is one of the more common complications that can occur with the vaccination.
Inoculation is derived from the Latin "in + oculus" (eye). Though "innoculation/innoculate" (with a double "nn" rather than a single "n") is sometimes seen, this is incorrect, possibly erroneously thought to be related to innocuous, which is derived from the Latin "in + nocuus" (not harmful). Inoculation originated as a method for the prevention of smallpox by deliberate introduction of material from smallpox pustules into the skin. This generally produced a less severe infection than naturally-acquired smallpox, but still induced immunity to it. This first method for smallpox prevention, smallpox inoculation, is now also known as variolation. Inoculation has ancient origins