Bacille Calmette-Guérin (BCG) is the only vaccine currently in use against TB, and is the collective term applied to a family of attenuated strains of Mycobacterium bovis, initially developed by Albert Calmette and Camille Guérin (hence the name) at the Pasteur Institute in Paris between 1908 and 1921. Subsequent strains have undergone further development through repeated subculturing in many laboratories around the world. While there are data showing that these different BCG strains have different immunogenicity in humans,133 it remains unknown whether they offer comparable protection against TB. Three parent strains of the BCG collective, Danish, Tokyo and Pasteur, now account for more than 90% of the TB vaccines used. The Pasteur strain of BCG serves as the reference strain of the vaccine and its complete genome sequence has been determined.134–136
According to the WHO/UNICEF Joint Reporting data from 2016, 155 of 194 member states recommended universal BCG vaccination at birth or within the first week of life, 25 countries recommended selective BCG vaccinations and 21 countries did not recommend routine vaccination.137 The BCG World Atlas provides detailed information on current and past BCG policies and practices.138
Beginning in 1926 in Quebec and 1933 in Saskatchewan, the National Research Council sponsored controlled trials of the safety and efficacy of BCG. Thereafter, BCG vaccination, either universal or selective, was promoted throughout Canada. As anti-TB drugs became available and incidence rates fell, BCG was discontinued in most populations. In recent years, its use has been limited to the First Nations and Inuit populations, where it has been part of a TB-elimination strategy. In these populations, BCG vaccination, as well as TB infection screening and treatment programs, have been associated with significant decreases in TB incidence.139,140 A summary of the usage of BCG in Canada over time is available on-line.141
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