This is a multicenter, randomized, controlled, open-label clinical trial testing the use of ozone auto-hemotherapy in hospitalized patients with Covid-19 pneumonia.

Eligible patients will be randomly assigned to receive either ozone auto-hemotherapy plus standard treatment, or standard treatment alone.

Patients in the ozone auto-hemotherapy group will receive treatment mixing 100-200ml of blood with ozone at a concentration of 40 μg / mL with a gas volume of 200 ml. Treatment will occur every 12h during 5 days. Standard treatment will be the one used in each hospital participating in the trial.

All analyses will be done according to the intention-to-treat principle

Inclusion Criteria:

• Diagnosis of COVID-19 confirmed by positive polymerase chain reaction (PCR) for Severe Acute Respiratory Syndrome (SARS-COV-2) in respiratory tract sample, plus pneumonia confirmed by imaging tests and arterial oxygen saturation (SpO2) <94% with ambient air or a partial pressure of oxygen to fraction of inspired oxygen (pO2/FiO2) ratio <300 mmHg or SpO2/FiO2 ≤ 315.
• Acceptance to participate in the study and signing of the informed consent.

Exclusion Criteria:

• Patients who have received treatment with any form of ozone therapy 6 months before admission to the hospital.
• Patients who have previously been treated and have experienced some type of adverse reaction to ozone therapy.
• Patients aware of having a deficiency of Glucose-6-phosphate dehydrogenase.
• Patients with clinically decompensated chronic comorbidities, independently of COVID-19.
• Patients suffering from any psychiatric disorder specified in axis I of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V), other than major depression.
• Patients who are not able to clearly understand the objectives and methodology of the study.
• Pregnant or lactating patients.