“The number of badgers killed in the TVR [test-vaccinate/remove] approach is likely to be low, as there are limits to the numbers of badgers that will be trapped and found to be infected, and only around half (49%) of infected badgers test positive for the disease [bovine tuberculosis].” (http://www.theguardian.com/environment/2014/jun/09/badger-cull-pilot-risks-spreading-bovine-tb)

49% accuracy being an improvement on indiscriminate culls.