DECRYPTION – A genetic study explains how the century-old bacillus has so-called “non-specific” effects, and modifies the immunity of children.
It started as an epidemiological curiosity. In the 1920s, in Sweden, the doctor Carl Näslund was surprised that children vaccinated with the BCG newly introduced into the country died two to three times less than the others. His hypothesis: the “bacillus of Calmette and Guérin”, a vaccine against tuberculosis developed at the Pasteur Institute in Lille and tested for the first time in 1921, would have “non-specific effects”. In other words, side effects, but desirable, which would protect against other pathogens than the one initially targeted. Since then, observations have accumulated, particularly in Africa: BCG (and other live virus vaccines such as the oral vaccine against poliomyelitis, or the vaccine against measles) could in the year following its injection prevent in new -born up to 30% of infections, especially respiratory.
Studies have shown that this protection “is linked to epigenetic modifications (changes in…