Vaccine compositions for boosting immunity to mycobacteria when administered in mid-life in a subject who has been vaccinated neonatally or in early childhood with BCG and in whom protective immunity has waned comprise one or more purified immunogenic proteins from Mycobacterium tuberculosis from a group of 30 proteins that stimulate T cell immunity and interferon-.gamma. secretion. A preferred protein is Ag85A, the secreted product (SEQ ID NO:31) of the Rv3084c gene. Also disclosed are methods for boosting immunity in such BCG-vaccinated subjects comprising administering an effective amount of the above vaccine composition.