1. Evidence of ongoing SARS-CoV-2 infection for more than 3 weeks, confirmed by a validated molecular assay or validated antigen assay. 2. Non-invasive ventilation (CPAP/BiPAP) or high-flow nasal oxygen therapy (WHO OSCI score of 5). 3. Endotracheal intubation and invasive mechanical ventilation (WHO OSCI score of ≥6)) or admission to intensive care. 4. Previous SARS-CoV-2 infection confirmed by a validated molecular assay or validated antigen assay. 5. Any condition, including findings in the patients’ medical history or in the pre-randomisation study assessments that in the opinion of the Investigator, constitute a risk or a contraindication for the participation of the patient into the study or that could interfere with the study objectives, conduct or evaluation. 6. Participation in previous clinical trials of SNG001. 7. Current or previous participation in another clinical trial where the patient has received a dose of an Investigational Medicinal Product (IMP) containing small molecules within 30 days or 5 half-lives (whichever is longer) prior to entry into this study or containing biologicals within 3 months prior to entry into this study. 8. Inability to use a nebuliser with a mouthpiece. 9. Inability to comply with the requirements for storage conditions of study medication in the home setting. 10. History of hypersensitivity to natural or recombinant IFN-β or to any of the excipients in the drug preparation. 11. Females who are breast-feeding, lactating, pregnant or intending to become pregnant.

1. Evidence of ongoing SARS-CoV-2 infection for more than 3 weeks, confirmed by a validated molecular assay or validated antigen assay. 2. Non-invasive ventilation (CPAP/BiPAP) or high-flow nasal oxygen therapy (WHO OSCI score of 5). 3. Endotracheal intubation and invasive mechanical ventilation (WHO OSCI score of ≥6)) or admission to intensive care. 4. Previous SARS-CoV-2 infection confirmed by a validated molecular assay or validated antigen assay. 5. Any condition, including findings in the patients’ medical history or in the pre-randomisation study assessments that in the opinion of the Investigator, constitute a risk or a contraindication for the participation of the patient into the study or that could interfere with the study objectives, conduct or evaluation. 6. Participation in previous clinical trials of SNG001. 7. Current or previous participation in another clinical trial where the patient has received a dose of an Investigational Medicinal Product (IMP) containing small molecules within 30 days or 5 half-lives (whichever is longer) prior to entry into this study or containing biologicals within 3 months prior to entry into this study. 8. Inability to use a nebuliser with a mouthpiece. 9. Inability to comply with the requirements for storage conditions of study medication in the home setting. 10. History of hypersensitivity to natural or recombinant IFN-β or to any of the excipients in the drug preparation. 11. Females who are breast-feeding, lactating, pregnant or intending to become pregnant.