Inclusion Criteria:  Subjects male or female, aged 18 and over. Acceptance to participate in the study by the signature of the informed consent by the subject or relative (if applicable). SARS-CoV-2 infection confirmed by reverse transcriptase -polymerase chain reaction (RT-PCR). SARS-CoV-2 pneumonia confirmed by chest X-ray. Patients with moderate or severe disease clinical presentation of the disease that require hospitalization. Being within 10 days of the initial COVID-19 related symptoms onset. Admission in the participating center within a 24hour period. Female patients of child-bearing age with a negative pregnancy test.  Exclusion Criteria:  COVID-19 patients that do not require hospitalization (outpatient setting). Patients who are participating in other therapeutic clinical trials. COVID-19 patients who have received convalescent plasma treatment. Critical disease COVID- 19 patients (respiratory failure, septic shock, and/or multiple organ dysfunction, admission PaO2/FIO2 ratio < 100). Previously snake bitten individuals that received any type of equine hyperimmune serum treatment. History of an allergic reaction due to contact or exposure to horses. Pregnant or breastfeeding women. Patients who, at the investigator´s discretion, are not likely to comply with study indications and procedures. Patients currently undergoing hemodialysis in a renal support program. Individuals who were previously classified by their treating physicians (prior to the COVID-19 diagnosis), of having an unfavorable prognosis with a short lifespan due to a concomitant disease other than the study disease.