- confirmed or highly suspected early stage severe acute respiratory syndrome coronavirus 2 (sars-cov-2), disease with clinical suspicion score >6/20, requiring hospitalization - suspected or confirmed convalescent severe acute respiratory syndrome coronavirus 2 (sars-cov-2), within the prior 4 weeks - age <18 years' old - inability to take medications orally - inability to provide written consent - known sensitivity/allergy to doxycycline or tetracyclines - current use of doxycycline for another indication - pregnancy - a known diagnosis of myasthenia gravis - history of clostridium difficile infection within past 12 months - sun sensitivity - individuals using medications which could lower doxycycline levels, including barbiturates, phenytoin, carbamazepine, warfarin - individuals using isotretinoin

- confirmed or highly suspected early stage severe acute respiratory syndrome coronavirus 2 (sars-cov-2), disease with clinical suspicion score >6/20, requiring hospitalization - suspected or confirmed convalescent severe acute respiratory syndrome coronavirus 2 (sars-cov-2), within the prior 4 weeks - age <18 years' old - inability to take medications orally - inability to provide written consent - known sensitivity/allergy to doxycycline or tetracyclines - current use of doxycycline for another indication - pregnancy - a known diagnosis of myasthenia gravis - history of clostridium difficile infection within past 12 months - sun sensitivity - individuals using medications which could lower doxycycline levels, including barbiturates, phenytoin, carbamazepine, warfarin - individuals using isotretinoin