In this study, the candidate vaccine LTB-SA7 will be tested for safety and immunogenicity in healthy adults.

LTB-SA7 is a candidate vaccine designed to induce immune response against toxins produced by Staphylococcus aureus. During the study, healthy adults will be randomized to receive one out of three different vaccine doses (starting with the group receiving the lowest dose), or a placebo. Participants will receive 2 injections, either two with candidate vaccine, 1 vaccine and 1 placebo, or 2 times placebo.

Inclusion Criteria:

1. Good general health by medical history, laboratory findings and physical examination as judged by the investigator before receiving the first injection.
2. Participant who is willing and able to comply with the requirements of the protocol (e.g., completion of the diary forms, return for follow-up visits).
3. Signed written informed consent obtained from the participant.
4. Participants between 18-50 years (inclusive) of age at the time of the first injection.
5. Negative urine pregnancy test for women of childbearing potential (WOCBP).
6. WOCBP must be willing to use a highly effective method of contraception during the trial.

Exclusion Criteria:

1. Health conditions that, in the opinion of the investigator, may interfere with optimal participation in the trial or place the participant at increased risk of adverse events.
2. Any deviation from the normal range in biochemistry or hematology blood tests clinically significant in the opinion of the investigator, measured at the screening visit.
3. Clinically significant abnormalities on physical examination.
4. Suspected or known hypersensitivity (including allergy) to any of the vaccine components or medical equipment whose use is foreseen in this trial.
5. History of allergy to any vaccine.
6. Clinical conditions representing a contraindication to intramuscular vaccination and blood draws (e.g., coagulation disorder).
7. Known or suspected impairment of immunological function e.g., documented Human Immunodeficiency Virus (HIV) infection, asplenia/splenectomy, or history of autoimmune disease or lymphoproliferative disorder.
8. Positive blood test for HBsAg, HCV, HIV-1/2.
9. History of systemic administration of immunosuppressive drugs, i.e., corticosteroids, (PO/IV/IM) within the last month prior to vaccination or for more than 14 consecutive days within 3 months prior to vaccination, until the last blood sampling visit (i.e., prednisone or equivalent ≥20 mg/day). Inhaled and topical steroids are allowed.
10. Administration of antineoplastic and immune-modulating agents or chemotherapy within 3 months prior to vaccination.
11. Planned or actual administration of any licensed vaccine within 14 days prior to each vaccination and 30 days after each vaccination. Note: In case an emergency mass vaccination for an unforeseen public health threat (e.g.: a pandemic) is organized by the public health authorities, the time period described above can be reduced, if necessary, for that vaccine provided it is licensed or authorized and used according to the local governmental recommendations and provided a written approval of the Sponsor is obtained.
12. Concurrently participating in another clinical trial, at any time during the trial period, in which the participant has been or will be exposed to an investigational or a non-investigational interventional vaccine/ product (pharmaceutical product).
13. Body Mass Index (BMI) ≤19 or ≥35
14. History of any chronic or progressive disease that according to judgment of the investigator could interfere with the trial outcomes or pose a threat to the participant's health.
15. Received an investigational or non-registered product (medicinal drug or vaccine), other than the trial vaccine within 3 months prior to 1st administration of trial vaccine, or planned use during the trial period.
16. Administration of immunoglobulin and/or any blood products within the three months preceding the first dose of trial vaccine.
17. Blood donation equal or greater to 500 mL of blood drawn within 3 months preceding the first or second vaccination or planned during the trial period as reported by the participant.
18. Use of any systemic antibiotic therapy within 1 week preceding each vaccination.
19. Participants with an elective surgical intervention, planned during the trial period until 1 month after 2nd vaccination.
20. Female participants lactating, pregnant, or intending to become pregnant as reported by the participant.