Cattle can also be vaccinated with the BCG vaccine. However, vaccination of cattle against TB is currently prohibited by EU legislation, mainly because BCG vaccination of cattle can interfere with the tuberculin skin test, the main diagnostic test for TB.

So let me get  this straight. We don't immunise cattle against TB preventing them getting it, because the vaccine prevents us from reliably telling if it worked or not and if they got TB despite the vaccine. So instead we'll kill Badgers despite knowing that incomplete removal of the badger population results in them spreading across the country carrying TB to places that don't currently have it.

This is one of those political problems with entrenched vested interests where the truth was thrown out long ago, right?