BCG is BCG vaccine for injection, and adults are not allowed to have BCG vaccine for injection. Injectable BCG is used to prevent childhood tuberculosis in children under 3 years old. There may be localized redness and swelling after BCG vaccination. BCG vaccine is contraindicated in patients with immunodeficiency and allergies. Adults are not allowed to take BCG injection. BCG injection is usually given intradermally and is mainly used for children under 3 years of age for the prevention of childhood tuberculosis, while BCG injection for adults has no preventive or curative effect. Adverse reactions such as local redness, swelling, lymphadenitis, osteomyelitis may occur after BCG injection. Patients with AIDS should not take BCG vaccine, which may lead to systemic BCG disease. It is contraindicated for patients with immunodeficiency and encephalopathy, which may lead to aggravation of the disease. It is prohibited for those who are allergic to BCG vaccine to prevent allergic symptoms such as generalized red rash and shock. Adults should not get injectable BCG vaccine, and injectable BCG vaccine can only be used for children under 3 years old.