Inclusion Criteria:  Informed consent: Signed written informed consent before inclusion in the study Full comprehension: Ability to comprehend the full nature and purpose of the study, including possible risks and side effects; ability to co-operate with the Investigator and to comply with the requirements of the entire study Sex and age: Healthy men and women, 18 - 55 years old, inclusive Negative SARS-CoV-2 serology test at screening (negative anti-S and anti-N) Negative SARS-CoV-2 qRT-PCR in the 72 h before treatment (test on day -3 or -2 or -1 with result before treatment) Body Mass Index: 18.5-30 kg/m2, inclusive, at screening Vital signs: Systolic blood pressure 90-139 mmHg, diastolic blood pressure 60-90 mmHg, heart rate 50-100 bpm, measured after 5 min at rest in the supine position ECG: Electrocardiogram without clinically significant abnormalities at screening  Contraception and fertility: Women of child-bearing potential must be using at least one of the following reliable methods of contraception and confirm to use adequate contraception during the study:  Hormonal oral or implantable or transdermal, or injectable contraceptives for at least 2 months before the screening visit; A non-hormonal intrauterine device or female condom with spermicide or contraceptive sponge with spermicide or diaphragm with spermicide or cervical cap with spermicide for at least 2 months before the screening visit A male sexual partner who agrees to use a male condom with spermicide A sterile sexual partner A same sex partner Female participants of non-child-bearing potential or in post-menopausal status for at least 1 year will be admitted. For all women, urine pregnancy test result must be negative at screening and day 1  Exclusion Criteria:  Physical findings: Clinically significant abnormal physical findings which could interfere with the objectives of the study Allergy: Ascertained or presumptive hypersensitivity to the active principle and/or ingredients of the investigational products; history of anaphylaxis to drugs or allergic reactions likely to be exacerbated by any component of the investigational products in the Investigator's opinion Concomitant medications: Medications, including over the counter (OTC) medications and herbal remedies, for 2 weeks before screening and immunoglobulin or blood products for 6 months before screening (except contraceptives or a single use of paracetamol, aspirin, or combination OTC products containing paracetamol with an antihistamine, or OTC non-steroidal anti-inflammatory drugs (NSAIDs) at a dose equal or lower than that recommended on the package; vitamins and nutritional supplements, if regularly taken before the study, are also allowed) Monoclonal Antibodies (mAb): Previous intake of a mAb within 6 months, or 5 antibody half-life, whichever is longer, before study start Transient acute illness: Acute (time-limited) illness, including fever above 37.5°C on the day before or on the day of the planned treatment; subjects excluded for transient acute illness may be dosed if illness resolves within the screening period or may be rescreened once Diseases: Significant history of renal, hepatic, gastrointestinal, cardiovascular, respiratory, skin, haematological, endocrine, psychiatric or neurological diseases that may interfere with the aim of the study or increase subjects risks; history of malignancy in the last 5 years  SARS CoV-2 or COVID-19:  Participants with any confirmed current or previous COVID-19 infection at screening, or at day -1 or day 1 Participant with clinical signs or symptoms consistent with COVID-19, e.g. fever, dry cough, dyspnoea, sore throat, fatigue or confirmed infection by appropriate laboratory test within the last 4 weeks before/at screening or at day -1 or day 1 Any prior intake of investigational or licenced vaccine indicated for the prevention of SARS CoV-2 or COVID-19 or expected intake during follow-up period Has been reported as a case (confirmed or probable) of COVID-19 from the regional health system Immunodeficiency due to illness, including HIV infection (positivity to anti-HIV-Ab), or due to drugs, including any course of glucocorticoid therapy exceeding 2 weeks of prednisone or equivalent within 6 months before screening. Infections: History of active infection with hepatitis B or C or positive test result for anti-HCV-Ab or HBsAg or anti-HBc-Ab at screening; history of infection with SARS or MERS Laboratory analyses: Abnormal laboratory values that in the opinion of the Investigator are clinically significant Investigative drug studies: Participation in the evaluation of any investigational product for 6 months before this study Blood donation: blood donations for 3 months before the study, during the study and in the 3 months after the end of the study Drug test: positive drug test at screening or day -1 Drug, alcohol: history of drug or alcohol abuse within 6 months before screening Pregnancy (women only): positive or missing pregnancy test at screening or day 1; pregnant or lactating women Other: Any condition that might compromise study subject's safety or interfere with the study evaluations or interpretation of subject's safety or study results