1. known current pregnancy. 2. history of sars-cov-2 infection. 3. receipt of a sars-cov-2 vaccination or monoclonal antibody. 4. unable to complete online questionnaires or adhere to study requirements. 5. consume more than 1000 iu per day of vitamin d from all supplemental sources combined (individual vitamin d supplements, calcium plus vitamin d supplements, medications with vitamin d \[e.g., fosamax plus d\], and multivitamins) in the past 4 weeks. 6. use of prescription vitamin d treatments (calcitriol \[rocaltrol, calcitrol, vectical, calcijex\] or paricalcitol \[zemplar\]). 7. consume supplements with more than 1200 mg calcium per day. 8. known diagnosis of hypercalcemia or a condition associated with vitamin d hypersensitivity. 9. prior diagnosis of cancer \*and\* currently undergoing radiation, chemotherapy, or immunotherapy. 10. kidney failure or dialysis; severe liver disease or cirrhosis. 11. any parathyroid condition. 12. use of medications for seizures or epilepsy. examples: carbamazepine (carbatrol, tegretol), phenytoin (dilantin, phenytek), valproic acid (depakene), oxcarbazepine (oxtellar, trileptal), phenobarbital, topiramate (topamax). 13. use of digoxin. 14. inability to receive an overnight express mail shipment of study pills at a home address. 15. participation in other covid-19 trials.

1. known current pregnancy. 2. history of sars-cov-2 infection. 3. receipt of a sars-cov-2 vaccination or monoclonal antibody. 4. unable to complete online questionnaires or adhere to study requirements. 5. consume more than 1000 iu per day of vitamin d from all supplemental sources combined (individual vitamin d supplements, calcium plus vitamin d supplements, medications with vitamin d \[e.g., fosamax plus d\], and multivitamins) in the past 4 weeks. 6. use of prescription vitamin d treatments (calcitriol \[rocaltrol, calcitrol, vectical, calcijex\] or paricalcitol \[zemplar\]). 7. consume supplements with more than 1200 mg calcium per day. 8. known diagnosis of hypercalcemia or a condition associated with vitamin d hypersensitivity. 9. prior diagnosis of cancer \*and\* currently undergoing radiation, chemotherapy, or immunotherapy. 10. kidney failure or dialysis; severe liver disease or cirrhosis. 11. any parathyroid condition. 12. use of medications for seizures or epilepsy. examples: carbamazepine (carbatrol, tegretol), phenytoin (dilantin, phenytek), valproic acid (depakene), oxcarbazepine (oxtellar, trileptal), phenobarbital, topiramate (topamax). 13. use of digoxin. 14. inability to receive an overnight express mail shipment of study pills at a home address. 15. participation in other covid-19 trials.

known current pregnancy. history of sars-cov-2 infection. receipt of a sars-cov-2 vaccination or monoclonal antibody. unable to complete online questionnaires or adhere to study requirements. consume more than 1000 iu per day of vitamin d from all supplemental sources combined (individual vitamin d supplements, calcium plus vitamin d supplements, medications with vitamin d [e.g., fosamax plus d], and multivitamins) in the past 4 weeks. use of prescription vitamin d treatments (calcitriol [rocaltrol, calcitrol, vectical, calcijex] or paricalcitol [zemplar]). consume supplements with more than 1200 mg calcium per day. known diagnosis of hypercalcemia or a condition associated with vitamin d hypersensitivity. prior diagnosis of cancer *and* currently undergoing radiation, chemotherapy, or immunotherapy. kidney failure or dialysis; severe liver disease or cirrhosis. any parathyroid condition. use of medications for seizures or epilepsy. examples: carbamazepine (carbatrol, tegretol), phenytoin (dilantin, phenytek), valproic acid (depakene), oxcarbazepine (oxtellar, trileptal), phenobarbital, topiramate (topamax). use of digoxin. inability to receive an overnight express mail shipment of study pills at a home address. participation in other covid-19 trials.

known current pregnancy. history of sars-cov-2 infection. receipt of a sars-cov-2 vaccination or monoclonal antibody. unable to complete online questionnaires or adhere to study requirements. consume more than 1000 iu per day of vitamin d from all supplemental sources combined (individual vitamin d supplements, calcium plus vitamin d supplements, medications with vitamin d [e.g., fosamax plus d], and multivitamins) in the past 4 weeks. use of prescription vitamin d treatments (calcitriol [rocaltrol, calcitrol, vectical, calcijex] or paricalcitol [zemplar]). consume supplements with more than 1200 mg calcium per day. known diagnosis of hypercalcemia or a condition associated with vitamin d hypersensitivity. prior diagnosis of cancer *and* currently undergoing radiation, chemotherapy, or immunotherapy. kidney failure or dialysis; severe liver disease or cirrhosis. any parathyroid condition. use of medications for seizures or epilepsy. examples: carbamazepine (carbatrol, tegretol), phenytoin (dilantin, phenytek), valproic acid (depakene), oxcarbazepine (oxtellar, trileptal), phenobarbital, topiramate (topamax). use of digoxin. inability to receive an overnight express mail shipment of study pills at a home address. participation in other covid-19 trials.

1. known current pregnancy. 2. history of sars-cov-2 infection. 3. receipt of a sars-cov-2 vaccination or monoclonal antibody. 4. unable to complete online questionnaires or adhere to study requirements. 5. consume more than 1000 iu per day of vitamin d from all supplemental sources combined (individual vitamin d supplements, calcium plus vitamin d supplements, medications with vitamin d [e.g., fosamax plus d], and multivitamins) in the past 4 weeks. 6. use of prescription vitamin d treatments (calcitriol [rocaltrol, calcitrol, vectical, calcijex] or paricalcitol [zemplar]). 7. consume supplements with more than 1200 mg calcium per day. 8. known diagnosis of hypercalcemia or a condition associated with vitamin d hypersensitivity. 9. prior diagnosis of cancer *and* currently undergoing radiation, chemotherapy, or immunotherapy. 10. kidney failure or dialysis; severe liver disease or cirrhosis. 11. any parathyroid condition. 12. use of medications for seizures or epilepsy. examples: carbamazepine (carbatrol, tegretol), phenytoin (dilantin, phenytek), valproic acid (depakene), oxcarbazepine (oxtellar, trileptal), phenobarbital, topiramate (topamax). 13. use of digoxin. 14. inability to receive an overnight express mail shipment of study pills at a home address. 15. participation in other covid-19 trials.

1. known current pregnancy. 2. history of sars-cov-2 infection. 3. receipt of a sars-cov-2 vaccination or monoclonal antibody. 4. unable to complete online questionnaires or adhere to study requirements. 5. consume more than 1000 iu per day of vitamin d from all supplemental sources combined (individual vitamin d supplements, calcium plus vitamin d supplements, medications with vitamin d [e.g., fosamax plus d], and multivitamins) in the past 4 weeks. 6. use of prescription vitamin d treatments (calcitriol [rocaltrol, calcitrol, vectical, calcijex] or paricalcitol [zemplar]). 7. consume supplements with more than 1200 mg calcium per day. 8. known diagnosis of hypercalcemia or a condition associated with vitamin d hypersensitivity. 9. prior diagnosis of cancer *and* currently undergoing radiation, chemotherapy, or immunotherapy. 10. kidney failure or dialysis; severe liver disease or cirrhosis. 11. any parathyroid condition. 12. use of medications for seizures or epilepsy. examples: carbamazepine (carbatrol, tegretol), phenytoin (dilantin, phenytek), valproic acid (depakene), oxcarbazepine (oxtellar, trileptal), phenobarbital, topiramate (topamax). 13. use of digoxin. 14. inability to receive an overnight express mail shipment of study pills at a home address. 15. participation in other covid-19 trials.

1. known current pregnancy. 2. history of sars-cov-2 infection with onset of symptoms more than 6 days before study entry. 3. receipt of a sars-cov-2 vaccination or monoclonal antibody. 4. unable to complete online questionnaires or adhere to study requirements. 5. consume more than 400 iu per day of vitamin d from all supplemental sources combined (individual vitamin d supplements, calcium plus vitamin d supplements, medications with vitamin d [e.g., fosamax plus d], and multivitamins) in the past 4 weeks. 6. known diagnosis of hypercalcemia or a condition associated with vitamin d hypersensitivity. 7. prior diagnosis of cancer *and* currently undergoing radiation, chemotherapy or immunotherapy. 8. kidney failure or dialysis; severe liver disease or cirrhosis. 9. unstable, transient, or group (6 or more adults) living arrangement. 10. participation in other covid-19 trials.

1. known current pregnancy. 2. history of sars-cov-2 infection with onset of symptoms more than 6 days before study entry. 3. receipt of a sars-cov-2 vaccination or monoclonal antibody. 4. unable to complete online questionnaires or adhere to study requirements. 5. consume more than 400 iu per day of vitamin d from all supplemental sources combined (individual vitamin d supplements, calcium plus vitamin d supplements, medications with vitamin d [e.g., fosamax plus d], and multivitamins) in the past 4 weeks. 6. known diagnosis of hypercalcemia or a condition associated with vitamin d hypersensitivity. 7. prior diagnosis of cancer *and* currently undergoing radiation, chemotherapy or immunotherapy. 8. kidney failure or dialysis; severe liver disease or cirrhosis. 9. unstable, transient, or group (6 or more adults) living arrangement. 10. participation in other covid-19 trials.