Lay Description

To determine whether metformin (MET) can improve the immune response to the pneumococcal conjugate vaccine (PCV-13) in older adults.


IRB Number
NCT Number
Open to Enrollment


Eligible Ages
Between 63 Years and 90 Years
Eligible Genders
Accepts Healthy Volunteers

Inclusion Criteria

  1. Age 63 to 89 years of age
  2. No history of pneumococcal vaccinations
  3. Able to take oral medications
  4. Able to provide informed consent
  5. Not currently taking metformin

Exclusion Criteria

  1. Previous vaccination with any pneumococcal vaccine
  2. Metformin within the last 6 months
  3. Contraindication for PCV13
  4. History of severe adverse reaction associated with any vaccine component
  5. Residence in long-term care facility
  6. Diagnosis of diabetes (diagnosis of pre-diabetes okay)
  7. Chronic renal disease (or eGFR <50 mL/min) or renal failure (defined as receipt of renal dialysis or transplant) or nephrotic syndrome
  8. History of adverse reaction or contraindications associated with metformin
  9. Recent history or plan for radiocontrast
  10. Self-reported dementia or severe cognitive impairment
  11. Receipt of blood products within 6 months before enrollment
  12. History of heart disease (New York Heart Classification greater than class II; more than non-specific ST-T wave changes on the ECG)
  13. History of chronic obstructive pulmonary disease
  14. Poorly controlled blood pressure (systolic BP>160, diastolic BP>90 mmHg)
  15. History of an immunodeficiency
  16. Use of use of investigational products, antibiotics, probiotics, or systemic immunosuppressive therapy (systemic steroids) within 1 month of study start; patients who are taking these medications chronically, with no expected discontinuation during the study period would not be considered ineligible.
  17. Treatment with anticoagulants (warfarin)
  18. Donated blood within the last 2 months
  19. Subject is considered unsuitable for the study in the opinion of the investigator for any other reason

Study Design

Arm Groups

Study Contact

Grace Lee
(210) 567-8355

Grace Lee
(210) 567-8355

Principal Investigator
Grace Lee