This is a first-in-human, phase I/IIa, randomized, controlled, observer-blinded, dose-escalation, multicentre clinical trial to evaluate safety and immunogenicity of COVID-19 HIPRA vaccine in adult healthy volunteers.

The study population includes 30 healthy adults aged 18-39 which will be distributed in 3 cohorts, receiving three different doses of antigen, 10 µg, 20 µg and 40 µg. In each cohort, patients will be randomized in ratio of 10:2 test:commercial vaccine, following an staggered enrolment with a sentinel subject in each cohort. Each participant will receive 2 immunisations separated by 21 days, and will be followed for 48 weeks after the second dose

Inclusion Criteria:

• Adults males or females between 18-39 years of age at the day of screening.
• Willing and able to comply with scheduled visits, laboratory test, complete diaries and other study procedures.
• Body Mass Index 18 to 40 Kg/m2 at screening.
• COVID19 negative PCR test and negative serum IgG binding antibody response to the SARS-CoV-2 S glycoprotein at screening or prior the first vaccination.
• Willing to avoid all other vaccines within 4 weeks before and after each injection. Seasonal influenza vaccination is allowed if it is received at least 14 days before or after the vaccination.
• Women of childbearing potential must have a negative pregnancy test in urine before the inclusion of the study and prior to each vaccination.
• If female of childbearing potential, willing to use highly effective contraceptive methods or have practiced sexual abstinence from the screening visit until 8 weeks after the last injection.
• If male and not sterilized, willing to avoid impregnating female partners from screening until 18 weeks after last injection.
• Willing and able to provide written informed consent prior the initiation of any study procedures.

Exclusion Criteria:

• Pregnant or lactating or intending to become pregnant or plans to breastfeed during the study.
• Positive pregnancy test at screening or prior to each vaccination.
• Any medical disease (acute, subacute, intermittent or chronic) or condition that in the opinion of the investigator compromise the volunteer's safety, preclude vaccination or compromise interpretation of the results.
• History of serious psychiatric condition likely to affect participation in the study (e-g- ongoing severe depression, history of admission to an in-patient psychiatric facility, recent suicidal ideation, history of suicide attempt, bipolar disorder, personality disorder, alcohol and drug dependency, severe eating disorder, psychosis, use of mood stabilisers or antipsychotic medication).
• History of respiratory disease (e.g., chronic obstructive pulmonary disease (COPD) and asthma) requiring any daily medications currently or any treatment of respiratory disease exacerbations (e.g., asthma exacerbation) in the last 5 years.
• History of significant cardiovascular disease including hypertension (e.g., congestive heart failure, cardiomyopathy, ischemic heart disease) or history of myocarditis or pericarditis as an adult.
• History of neurological or neurodevelopmental conditions (e.g., migraines, epilepsy, stroke, seizures in the last 3 years, encephalopathy, focal neurologic deficits, Guillain-Barré syndrome, encephalomyelitis or transverse myelitis).
• Ongoing malignancy or recent diagnosis of malignancy in the last five years excluding basal cell and squamous cell carcinoma of the skin, which are allowed.
• Any confirmed or suspected immunosuppressive or immunodeficient state, including HIV infection; asplenia; recurrent severe infections.
• Any autoimmune or immunodeficiency disease/condition (iatrogenic or congenital).
• Acute illness within 72 hours prior each vaccination that in the opinion of the investigator may interfere the evaluation of safety parameters.
• Usage of any investigational drug ≤ 90 days prior to study entry or plan to participate in another research involving an investigational product (drug/biologic/device) within 12 months after the first study vaccination.
• History of hypersensitivity or severe allergic reaction including anaphylaxis, generalized urticarial, angioedema and other significant reactions related to food, drugs, vaccines or pharmaceutical agents.
• History of allergic disease or reactions likely to be exacerbated by any component of the COVID-19 vaccine HIPRA.
• Use of any immunosuppressant, glucocorticoids, or other immune-modifying drugs within 2 months prior to first study vaccination; or anticipation of the need for immunosuppressive treatment within 6 months after last vaccination.
• Received immunoglobulin, blood-derived products, or other immunosuppressant drugs within 90 days prior to first study vaccination.
• Known disturbance of coagulation (iatrogenic or congenital) or blood dyscrasias.
• Known bleeding disorder (e-g- factor deficiency, coagulopathy or platelet disorder), or prior history of significant bleeding or bruising following IM injections or venepuncture.
• Chronic liver disease.
• Positive test for HIV types 1 or 2 infection, hepatitis B surface antigen (HBsAg), or hepatitis C virus antibodies (HCV Abs) at screening.
• Suspected or known current alcohol abuse or any other substances abuse (except tobacco).
• History of COVID-19 infection.
• Receipt of medications intended to prevent COVID-19.
• Ever received an experimental vaccine against COVID-19.
• Close contact of anyone known to have SARS-CoV-2 infection within 15 days prior to screening visit.
• Being directly involved in the conduct of the study.
• Any condition and/or laboratory finding that at the investigator consideration would interfere with the study or put at risk the participant.

To be decided