TB vaccines can vary greatly, study finds. But does that mean some are less protective?
It all started with a bit of bacteria swiped from the udder of a tuberculous French cow. Initially, it was just another livestock sample, a speck of virulence lounging in a Paris lab. But then it began to change. Two scientists had brought some of it to Lille, near the Belgian border, and had fed it a concoction of potato, glycerin, and ox bile. The bugs liked this witches’ brew, and multiplied, and multiplied again.
After years away from live animal hosts, the bacterium got used to its cushy lab-dish life and lost its barnyard edge. Enough of its tough old self remained to trigger a body’s immune defenses, but not enough to make a healthy person sick. Perfect for a microbial training drill. Word spread. Scientists made pilgrimages to France, to take home some defused bovine tuberculosis of their own — and what began as an udder-swab in 1902 ended up yielding one of the world’s most widely used vaccines, now given to some 100 million infants globally each year.
