Inclusion Criteria:  Male or female, by birth, ≥ 18 years old at Screening. Willing and able to comply with scheduled visits, laboratory tests, complete diaries, and other study procedures. Body Mass Index (BMI) between 18 to 40 kg/m2. Has received a complete COVID-19 vaccination programme (two administrations, prime and boosting) at least 182 days and with a maximum of 365 days before Screening with Comirnaty vaccine. Has a negative COVID-19 polymerase chain reaction (PCR) test at Screening. Willing to avoid all other vaccines within 4 weeks before and after vaccination in this study (Day 0). Seasonal influenza vaccination is allowed if it is received at least 14 days before or after vaccination. Willing to refrain from blood donation during the study. Women of childbearing potential must have a negative urine pregnancy test at Screening and prior to vaccination. Women of childbearing potential must be willing to use highly effective contraceptive methods or have practiced sexual abstinence from the screening visit until 8 weeks after the vaccination. Males who are not sterilised, must be willing to avoid impregnating female partners from Screening until 8 weeks after vaccination. 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 vaccination day. Any medical disease (acute, subacute, intermittent, or chronic) or condition that in the opinion of the Investigator compromises the subject's safety, preclude vaccination or compromises interpretation of the results. Ongoing serious psychiatric condition likely to affect participation in the study (e.g., ongoing severe depression, recent suicidal ideation, 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]) requiring daily medications currently or any treatment of respiratory disease exacerbations (e.g., asthma exacerbation) in the last 6 months. History of significant cardiovascular disease (e.g., congestive heart failure, cardiomyopathy, ischemic heart disease) or history of myocarditis or pericarditis as an adult. Controlled hypertension will be permitted at the discretion of the Investigator. History of neurological or neurodevelopmental conditions (e.g., 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 autoimmune, immunosuppressive or immunodeficiency disease/condition (iatrogenic or congenital), including human immunodeficiency virus (HIV) infection, asplenia, or recurrent severe infections. Acute illness within 72 hours before vaccination day that, in the opinion of the Investigator may interfere the evaluation of safety parameters. Received investigational drug within 90 days before Screening or plans to participate in another interventional clinical study (drug/biologic/device) within 12 months after vaccination. History of hypersensitivity or severe allergic reactions, including anaphylaxis, generalised urticarial, angioedema and other significant reactions related to food, drugs, vaccines, or pharmaceutical agents, which are likely to be exacerbated by any component of the COVID-19 vaccine HIPRA (including the oil in water adjuvant equivalent to MF59C.1). Use of any immunosuppressant, glucocorticoids, or other immune-modifying drugs within 2 months before vaccination day; or anticipation of the need for immunosuppressive treatment within 182 days after vaccination. Received immunoglobulin, blood-derived products, or other immunosuppressant drugs within 90 days before vaccination (Day 0). Known disturbance of coagulation (iatrogenic or congenital) or blood dyscrasias. Known bleeding disorder (e.g., factor deficiency, coagulopathy, or platelet disorder), (iatrogenic or congenital), blood dyscrasias, or prior history of significant bleeding or bruising following intramuscular (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.  Ever been included in a trial with an experimental vaccine against COVID-19. Close contact with anyone known to have SARS-CoV-2 infection within 15 days before Screening. Scheduled elective surgery during the study. Life expectancy of less than 12 months. Any condition and/or laboratory finding that, in the Investigators opinion, would interfere with the study or put the subject at risk.