Investigator vaccinated 76 healthy BCG-naive participant with BCG, while 3 participants received. Half of BCG-vaccinated participants (n = 38) received an incremental dose of metformin for 6 days (up to 1,000 mg twice daily on day 6). On the day 0 (total 20; n = 10 for BCG vaccination, n = 10 for BCG vaccination plus taking metformin), day 14 (total 30; n=15 for BCG vaccination, n = 15 for BCG vaccination plus taking metformin), day 90 (total 26; n = 13 for BCG vaccination, n=13 for BCG vaccination plus taking metformin) of BCG vaccination, PBMCs were isolated, restimulated with C. albicans or Mycobacterium tuberculosis.

Inclusion Criteria:

• Healthy BCG-naive participants.
• The ages range from 20 to 45.
• Participants without any infections or immune deficiencies.

Exclusion Criteria:

• Participants when infections or other illnesses occurred during the clinical trial.
• Participants who have a fever of unknown causes during the clinical trial.
• Participants who have gotten other vaccines during the clinical trial.