BCG VACCINE  

PREPARATION: BCG, or Bacille Calmette-Gu�rin, is a vaccine for tuberculosis (TB) disease. BCG (Bacillus of Calmette and Guerin) is named after the two Frenchmen who developed it. BCG consists of a live attenuated strain derived from Mycobacterium bovis, which has been attenuated by 239  successive in vitro subcultures in glycerol-bile-potato medium for over 13 years. 

PRESERVATION: It is available as a freeze-dried preparation for injection. The intact ampoule must be refrigerated at 2 to 8�C. The reconstituted vaccine also must be refrigerated and protected from exposure to light. It must be used within 2 hours of reconstitution. 

INDICATIONS: It is indicated in primary prophylaxis against tuberculosis in all newborn infants, contacts of those with active pulmonary tuberculosis, health staff those who handle animal species known to be susceptible to tuberculosis, and tuberculin negative children between 10-14 years of age. BCG is no longer recommended by CDC for health care workers or other adults who are likely to be exposed to TB. 

ADMINISTRATION AND DOSE: Adult dose: 0.1 ml; infant under 3 months: 0.05 ml by intradermal injection at the insertion of deltoid muscle on the humerus. 0.05-0.1mg of bacilli from a freeze-dried culture diluted in distilled water to a volume of 0.1ml is given intradermally. For percutaneous administration, one drop of vaccine is placed on the skin and introduced through the skin by multiple punctures with a bifurcated or other type of needle. It is given routinely at birth in many countries (including India) with a high incidence of tuberculosis. 

READING: A papule appears at the site of inoculation in 3-6 weeks and increases in size for a further 2-3 weeks. A shallow ulcer up to 1 cm in diameter may form. The lesion begins to subside about two months after inoculation and eventually leaves only a small scar. Most tuberculin-negative individuals when vaccinated with BCG become tuberculin positive in 2 months and 95% remain tuberculin positive even after four years. If tuberculin reactivity does not occur in three months, the subject should be revaccinated. 
 
EFFECTS: The vaccine prevents disseminated tuberculosis in newborns (60-80% effectiveness) but fails to protect against pulmonary tuberculosis in adults. BCG vaccination’s greatest utility appears to be in the prevention of meningeal and miliary TB in children.  

SIDE EFFECTS: BCG has been associated with severe or prolonged ulceration at the vaccination site, regional adenitis, disseminated BCG infection, and osteitis. Severe ulceration and adenitis occur among approximately 1%-10% of vaccinees, although disseminated infections and osteitis are quite rare. 

CONTRAINDICATIONS: BCG vaccines should not be given to persons who are immunocompromised as a result of immune deficiency diseases (e.g. HIV), leukemia, lymphoma, or generalized malignancy or who are immunosuppressed as a result of therapy with corticosteroids, alkylating drugs, antimetabolites, radiation, or suffering from generalized septic skin conditions, tumours of reticuloendothelial system. 

LIMITATIONS: Multiple field trials have failed to conclusively demonstrate protective efficacy of BCG against uncomplicated TB. Previous vaccination often causes a positive skin test reaction. BCG does not protect from infection by M. tuberculosis. It is not effective in preventing reactivation tuberculosis. 

OTHER APPLICATIONS: Nonspecific immune stimulation of cancer patients with adjuvants such as BCG has been tried for many years. Intralesional BCG can cause regression of melanoma and bladder tumors by nonspecific stimulation of cell-mediated immunity. It has been recently shown that some protection is given against leprosy after a second BCG injection. BCG has also been experimentally used as expression vectors.