The invention discloses a live modified Mycobacterium bovis-BCG strain in which the lsr2 gene is inactivated or its expression is reduced and a pharmaceutical composition comprising the same for the treatment or prophylaxis of a mammal against challenge by mycobacteria or against cancer. The invention further discloses a method for the treatment or prophylaxis of a mammal against challenge by Mycobacterium tuberculosis or Mycobacterium bovis or against cancer by administering to the mammal the live modified Mycobacterium bovis-BCG strain or the pharmaceutical composition of the present invention.
