Vitamin D Supplementation and Acute Respiratory Infection in Older Long-Term Care Residents

Inclusion Criteria: * Age 60+ years * Resides in nursing home Exclusion Criteria: * Terminal illness (expected survival \<6 months) * Anticipated discharge within 12 months * Unable to take whole or crushed tablets * Active cancer, except squamous/basal cell carcinoma * Severe malnutrition (body mass index \<18 kg/m2) * Current immunosuppressive medications (including corticosteroids) * Renal failure (estimated glomerular filtration rate \< 15 mL/min/1.73m2) * Currently taking \>1,000 IU/d vitamin D supplementation * History (or strong family history) of kidney stones * History of sarcoidosis or other granulomatous disorders associated with hypercalcemia * Elevated baseline hypercalcemia (albumin-adjusted serum calcium \>10.5 mg/dL) * Baseline serum 25OHD level ≥ 100 nmol/L * Inability to provide informed consent and no available healthcare legally authorized representative * Inability of participant or legally authorized representative to speak/understand English