[10][11] In countries where tuberculosis or leprosy is common, one dose is recommended in healthy babies as soon after birth as possible.

[9] Although no harmful effects on the fetus have been observed, there is insufficient evidence about the safety of BCG vaccination during pregnancy.

[19] The most controversial aspect of BCG is the variable efficacy found in different clinical trials, which appears to depend on geography.

Still, those trials conducted elsewhere have shown no protective effect, and efficacy appears to fall the closer one gets to the equator.

The development of new vaccines with greater efficacy against adult pulmonary tuberculosis may be needed to make substantial progress.

[35][36] By 2014, more than eight different considered biosimilar agents or strains used to treat nonmuscle-invasive bladder cancer.

A reactive tuberculin skin test is a contraindication to BCG due to the risk of severe local inflammation and scarring; it does not indicate immunity.

Numerous medical studies on the treatment of these abscesses with antibiotics have been done with varying results, but the consensus is once pus is aspirated and analysed, provided no unusual bacilli are present, the abscess will generally heal on its own in a matter of weeks.

The insertion to the deltoid muscle is most frequently used because the local complication rate is smallest when that site is used.

If given subcutaneously, it may induce local infection and spread to the regional lymph nodes, causing either suppurative (production of pus) or nonsuppurative lymphadenitis.

[42] Uncommonly, breast and gluteal abscesses can occur due to haematogenous (carried by the blood) and lymphangiomatous spread.

[45] When systemic involvement occurs, liver and lungs are the first organs to be affected (1 week [median] after the last BCG instillation).

[46] If BCG is accidentally given to an immunocompromised patient (e.g., an infant with severe combined immune deficiency), it can cause disseminated or life-threatening infection.

[51] BCG is prepared from a strain of the attenuated (virulence-reduced) live bovine tuberculosis bacillus, Mycobacterium bovis, that has lost its ability to cause disease in humans.

Pacis BCG, made from the Montréal (Institut Armand-Frappier) strain,[99] was first marketed by Urocor in about 2002.

Statens Serum Institut in Denmark has marketed a BCG vaccine prepared using Danish strain 1331.

According to a UNICEF report published in December 2015, on BCG vaccine supply security, global demand increased in 2015 from 123 to 152.2 million doses.

To improve security and to [diversify] sources of affordable and flexible supply," UNICEF awarded seven new manufacturers contracts to produce BCG.

[104] By April 2012 the FDA had found dozens of documented problems with sterility at the plant including mold, nesting birds and rusted electrical conduits.

[103] The resulting closure of the plant for over two years caused shortages of bladder cancer and tuberculosis vaccines.

[105] On 29 October 2014 Health Canada gave the permission for Sanofi to resume production of BCG.

[113] But in 1895, Theobald Smith presented differences between human and bovine tuberculosis, which he reported to Koch.

Their work included subculturing virulent strains of the tuberculosis bacillus and testing different culture media.

They noted a glycerin-bile-potato mixture grew bacilli that seemed less virulent and changed the course of their research to see if repeated subculturing would produce a strain that was attenuated enough to be considered for use as a vaccine.

It was subsequently discovered that the BCG administered there had been contaminated with a virulent strain that was being stored in the same incubator, which led to legal action against the vaccine's manufacturers.

[118] Dr. R. G. Ferguson, working at the Fort Qu'Appelle Sanatorium in Saskatchewan, was among the pioneers in developing the practice of vaccination against tuberculosis.

In Canada, more than 600 children from residential schools were used as involuntary participants in BCG vaccine trials between 1933 and 1945.

[122] Tentative evidence exists for a beneficial non-specific effect of BCG vaccination on overall mortality in low-income countries, or for its reducing other health problems including sepsis and respiratory infections when given early,[123] with greater benefit the earlier it is used.

[127] The University of Oxford Jenner Institute is conducting a study comparing the efficacy of injected versus inhaled BCG vaccine in already-vaccinated adults.

[136] On the other hand, a 5-month trial shows that re-vaccinating with BCG does not help prevent infection in healthcare workers.