1. acute coronavirus disease (covid-19) at baseline visit 2. patients who were treated in the intensive care unit because of covid-19 3. pregnancy/ breastfeeding 4. diabetes mellitus 5. pc19s symptoms that can be explained by an alternative diagnosis 6. history of severe medical conditions such as * concomitant acute infectious disease * gastrointestinal ulcer * liver disease/liver cirrhosis * malabsorption or condition after bariatric surgery * chronic airway disease * chronic heart failure \[new york heart association (nyha) iii and iv\] * neurological disorders * untreated hypothyroidism * significantly impaired glucuronidation * immunodeficiency or a chronically weakened immune system * mental disorders * active cancer * any other severe medical conditions that preclude participation as determined by responsible physician 7. current use of * immunosuppressive drugs * non-steroidal antiinflammatory drugs (nsaid) * fluoroquinolones * anticoagulation * any other drug that could exhibit clinically relevant interactions with the study medication (as described in fachinformation prednisolon stada®, predni h tablinen® zentiva or fachinformation vitamin b komplex hevert). the decision on the clinical relevance of the interactions is at the discretion of the clinical investigator. 8. systemic treatment with prednisolone for at least 7 days or any parenteral application since the end of the acute phase of covid-19; treatment with vitamins b1, b6, or b12 in doses equivalent to the dose of the study medi-cation for at least 7 days or any parenteral application since the end of the acute phase of covid-19; vitamin supplements containing vitamin b1, b6, or b12 should have been ceased at least 4 weeks prior to the inclusion of the study 9. known allergies and contraindications to the intervention drugs 10. need of care and/or peer dependency 11. nursing home residents 12. inability to understand the scope of the study, to follow study procedures and to give informed consent or to attend the study sites 13. participation in another interventional trial at the same time or within the past 3 months before enrolment 14. female patients considering to get pregnant during the first month of the trial and within 1 week after the last dose of study drug(s)

1. acute coronavirus disease (covid-19) at baseline visit 2. patients who were treated in the intensive care unit because of covid-19 3. pregnancy/ breastfeeding 4. diabetes mellitus 5. pc19s symptoms that can be explained by an alternative diagnosis 6. history of severe medical conditions such as * concomitant acute infectious disease * gastrointestinal ulcer * liver disease/liver cirrhosis * malabsorption or condition after bariatric surgery * chronic airway disease * chronic heart failure \[new york heart association (nyha) iii and iv\] * neurological disorders * untreated hypothyroidism * significantly impaired glucuronidation * immunodeficiency or a chronically weakened immune system * mental disorders * active cancer * any other severe medical conditions that preclude participation as determined by responsible physician 7. current use of * immunosuppressive drugs * non-steroidal antiinflammatory drugs (nsaid) * fluoroquinolones * anticoagulation * any other drug that could exhibit clinically relevant interactions with the study medication (as described in fachinformation prednisolon stada®, predni h tablinen® zentiva or fachinformation vitamin b komplex hevert). the decision on the clinical relevance of the interactions is at the discretion of the clinical investigator. 8. systemic treatment with prednisolone for at least 7 days or any parenteral application since the end of the acute phase of covid-19; treatment with vitamins b1, b6, or b12 in doses equivalent to the dose of the study medi-cation for at least 7 days or any parenteral application since the end of the acute phase of covid-19; vitamin supplements containing vitamin b1, b6, or b12 should have been ceased at least 4 weeks prior to the inclusion of the study 9. known allergies and contraindications to the intervention drugs 10. need of care and/or peer dependency 11. nursing home residents 12. inability to understand the scope of the study, to follow study procedures and to give informed consent or to attend the study sites 13. participation in another interventional trial at the same time or within the past 3 months before enrolment 14. female patients considering to get pregnant during the first month of the trial and within 1 week after the last dose of study drug(s)

acute coronavirus disease (covid-19) at baseline visit patients who were treated in the intensive care unit because of covid-19 pregnancy/ breastfeeding diabetes mellitus pc19s symptoms that can be explained by an alternative diagnosis history of severe medical conditions such as concomitant acute infectious disease gastrointestinal ulcer liver disease/liver cirrhosis malabsorption or condition after bariatric surgery chronic airway disease chronic heart failure [new york heart association (nyha) iii and iv] neurological disorders untreated hypothyroidism significantly impaired glucuronidation immunodeficiency or a chronically weakened immune system mental disorders active cancer any other severe medical conditions that preclude participation as determined by responsible physician current use of immunosuppressive drugs non-steroidal antiinflammatory drugs (nsaid) fluoroquinolones anticoagulation any other drug that could exhibit clinically relevant interactions with the study medication (as described in fachinformation prednisolon stada®, predni h tablinen® zentiva or fachinformation vitamin b komplex hevert). the decision on the clinical relevance of the interactions is at the discretion of the clinical investigator. systemic treatment with prednisolone for at least 7 days or any parenteral application since the end of the acute phase of covid-19; treatment with vitamins b1, b6, or b12 in doses equivalent to the dose of the study medi-cation for at least 7 days or any parenteral application since the end of the acute phase of covid-19; vitamin supplements containing vitamin b1, b6, or b12 should have been ceased at least 4 weeks prior to the inclusion of the study known allergies and contraindications to the intervention drugs need of care and/or peer dependency nursing home residents inability to understand the scope of the study, to follow study procedures and to give informed consent or to attend the study sites participation in another interventional trial at the same time or within the past 3 months before enrolment female patients considering to get pregnant during the first month of the trial and within 1 week after the last dose of study drug(s)

acute coronavirus disease (covid-19) at baseline visit patients who were treated in the intensive care unit because of covid-19 pregnancy/ breastfeeding diabetes mellitus pc19s symptoms that can be explained by an alternative diagnosis history of severe medical conditions such as concomitant acute infectious disease gastrointestinal ulcer liver disease/liver cirrhosis malabsorption or condition after bariatric surgery chronic airway disease chronic heart failure [new york heart association (nyha) iii and iv] neurological disorders untreated hypothyroidism significantly impaired glucuronidation immunodeficiency or a chronically weakened immune system mental disorders active cancer any other severe medical conditions that preclude participation as determined by responsible physician current use of immunosuppressive drugs non-steroidal antiinflammatory drugs (nsaid) fluoroquinolones anticoagulation any other drug that could exhibit clinically relevant interactions with the study medication (as described in fachinformation prednisolon stada®, predni h tablinen® zentiva or fachinformation vitamin b komplex hevert). the decision on the clinical relevance of the interactions is at the discretion of the clinical investigator. systemic treatment with prednisolone for at least 7 days or any parenteral application since the end of the acute phase of covid-19; treatment with vitamins b1, b6, or b12 in doses equivalent to the dose of the study medi-cation for at least 7 days or any parenteral application since the end of the acute phase of covid-19; vitamin supplements containing vitamin b1, b6, or b12 should have been ceased at least 4 weeks prior to the inclusion of the study known allergies and contraindications to the intervention drugs need of care and/or peer dependency nursing home residents inability to understand the scope of the study, to follow study procedures and to give informed consent or to attend the study sites participation in another interventional trial at the same time or within the past 3 months before enrolment female patients considering to get pregnant during the first month of the trial and within 1 week after the last dose of study drug(s)

acute coronavirus disease (covid-19) at baseline visit patients who were treated in the intensive care unit because of covid-19 pregnancy/ breastfeeding diabetes mellitus hypertension pc19s symptoms that can be explained by an alternative diagnosis history of severe medical conditions such as concomitant acute infectious disease gastrointestinal ulcer liver disease/liver cirrhosis malabsorption or condition after bariatric surgery chronic airway disease chronic heart failure [new york heart association (nyha) iii and iv] neurological disorders untreated hypothyroidism significantly impaired glucuronidation immunodeficiency or a chronically weakened immune system mental disorders active cancer any other severe medical conditions that preclude participation as determined by responsible physician current use of immunosuppressive drugs non-steroidal antiinflammatory drugs (nsaid) fluoroquinolones anticoagulation any other drug with a possible interaction with the study medication current or previous systemic treatment with any of the treatment drugs for at least seven days since covid-19 or any parenteral application known allergy and contraindications to the intervention drugs need of care and/or peer dependency nursing home residents inability to understand the scope of the study, to follow study procedures and to give informed consent or to attend the study sites participation in another interventional trial at the same time or within the past 3 months before enrolment female patients considering to get pregnant during the first month of the trial and within 1 week after the last dose of study drug(s)

acute coronavirus disease (covid-19) at baseline visit patients who were treated in the intensive care unit because of covid-19 pregnancy/ breastfeeding diabetes mellitus hypertension pc19s symptoms that can be explained by an alternative diagnosis history of severe medical conditions such as concomitant acute infectious disease gastrointestinal ulcer liver disease/liver cirrhosis malabsorption or condition after bariatric surgery chronic airway disease chronic heart failure [new york heart association (nyha) iii and iv] neurological disorders untreated hypothyroidism significantly impaired glucuronidation immunodeficiency or a chronically weakened immune system mental disorders active cancer any other severe medical conditions that preclude participation as determined by responsible physician current use of immunosuppressive drugs non-steroidal antiinflammatory drugs (nsaid) fluoroquinolones anticoagulation any other drug with a possible interaction with the study medication current or previous systemic treatment with any of the treatment drugs for at least seven days since covid-19 or any parenteral application known allergy and contraindications to the intervention drugs need of care and/or peer dependency nursing home residents inability to understand the scope of the study, to follow study procedures and to give informed consent or to attend the study sites participation in another interventional trial at the same time or within the past 3 months before enrolment female patients considering to get pregnant during the first month of the trial and within 1 week after the last dose of study drug(s)