This is a randomized, Multicenter, double-blind (subject, investigator, and Merck Research Laboratories (MRL) clinical personnel directly involved in the study), placebo-controlled, dose-ranging study in healthy adults 18 to 55 years of age. It is the first in man (FIM) study evaluating the tolerability and immunogenicity of the 0657nI S. aureus vaccine. For this Phase I study, approximately 120 healthy adults will be enrolled in the study and randomized to receive a single 0.5 mL vaccination of either 0657nI S. aureus vaccine (3 different dosage levels of 5 μg, 30 μg or 90 μg of the 0657nI vaccine) or saline placebo. Vaccine/placebo will be administered intramuscularly (IM) in the deltoid muscle. Because this study will be the first study evaluating the tolerability and immunogenicity of 0657nI S. aureus vaccine in humans, a dose-escalation phase will be conducted in a small number of subjects randomized in a 3:1 ratio (n=36, consisting of 9 subjects for each of 3 vaccine dosage levels and 9 placebo subjects) to evaluate the vaccine safety at increasing dose levels of the 0657nI protein in Panel A, before expanding the enrollment to the remaining 84 subjects in Panel B.

Depending on when the subject is enrolled into the study, the following will be completed: The subject will receive a single injection of SAV or placebo (an inactive substance) in the deltoid muscle of the upper arm. The subject will then be watched for 30 minutes after vaccination to monitor for allergic reactions. The subject will be asked to visit the study doctor either 6 or 9 times during the 3-month study period. Once enrolled, the subject will have blood drawn before receiving the vaccine (baseline) and up to 7 times after that at each of the required visits. The blood will be used for tests and/or for testing the subject's body's immune response to the SAV, to see if the subjects have developed immunity to S. aureus and if immunity continues up to 84 days. A Vaccination Report Card (VRC) will be provided to all participants. The participant will be asked to record oral temperatures and any reactions that occur at the SAV injection site every day for 5 days after vaccination. The participant will also be asked to record any physical adverse effects that they may experience, including headaches, nausea, muscle pain or aches, and fatigue every day for 14 days after vaccination. In additional all medications (including over the counter medications) taken during the 14 days post vaccination will be recorded and the VRC will be returned to the research staff after 14 days.

Inclusion Criteria:

• Subject is 18 to 55 years of age
• Subject is in good physical health based upon medical history, physical examination, and screening laboratory studies. NOTE: Lab studies will only be collected in Panel A, the dose-escalating portion of the study
• Subject is able to understand study procedures and agrees to participate in the study by providing written informed consent
• Subject is willing and able to participate in the entire study duration planned for 3 months (~84 days)
• Female subjects are required to have a negative urine pregnancy test immediately prior to study vaccination. Female subjects of childbearing potential must have been using an acceptable method of birth control for 2 weeks prior to enrollment, and agree to use an acceptable method of birth control for 1 month after vaccination. (Acceptable methods of birth control include use of hormonal contraceptives, intrauterine device (IUD), diaphragm with spermicide, contraceptive sponge, tubal ligation, condoms, or abstinence)

Exclusion Criteria:

• Subject suffers from a chronic skin condition that predisposes the individual to the development of chronic skin or soft-tissue infections (e.g., psoriasis, chronic granulomatous disease).
• Subject developed a serious infection (e.g., bacteremia, pneumonia, mediastinitis) attributed to S. aureus in the 12 months prior to screening
• Subject has a history of anaphylaxis to aluminum-containing adjuvant or other vaccine components
• Subject has a temperature of ≥100.4ºF (≥38.0ºC), oral equivalent, within 48 hours prior to receipt of 0657nI S. aureus vaccine/placebo
• Subject has received a live virus vaccine within 30 days prior to receipt of 0657nI S. aureus vaccine/placebo or is scheduled to receive vaccination with a live virus vaccine within 30 days following study entry
• Subject has received any other licensed vaccine (including non-live virus vaccines) within 14 days prior to receipt of 0657nI S. aureus vaccine/placebo or is scheduled to receive any other licensed vaccine (including non-live virus vaccines) within 30 days following study entry. (Note: Influenza vaccines may be administered during the study, but must be given at least 7 days prior to receipt of the study vaccine or at least 15 days after receipt of the study vaccine)
• Subject was administered immunoglobulin or blood product within 90 days prior to receipt of 0657nI S. aureus vaccine/placebo or is scheduled to receive such products within 30 days following study entry
• Subject has received treatment with systemic (intramuscular, oral, or intravenous) corticosteroids or another immunosuppressive medication (e.g., calcineurin inhibitors, mycophenolate, azathioprine) in the 14 days prior to receipt of 0657nI S. aureus vaccine/placebo or is anticipated to receive such medications for a chronic medical condition during the course of the study
• Subject has a condition that requires active medical intervention or monitoring to avert serious danger to the subject's health or well-being, such as diabetes mellitus, autoimmune disease, or clinically significant chronic medical conditions that are considered progressive, including but not limited to: coronary artery disease, congestive heart failure, cardiomyopathy, progressive valvular heart disease, chronic obstructive pulmonary disease, pulmonary fibrosis, active peptic ulcer disease, chronic renal disease, chronic hepatic disease, multiple sclerosis, progressive neuropathies, or seizure disorder requiring therapy in the past 3 years
• Subject has known or suspected impairment of immunologic function including, but not limited to, the following conditions: autoimmune disease, diabetes mellitus, end-stage renal disease, hepatic insufficiency/cirrhosis, splenectomy, or HIV/AIDS
• Subject has a condition in which repeated venipuncture or injections pose more than minimal risk for the subject, such as hemophilia, other severe coagulation disorders, or significantly impaired venous access
• Subject is currently pregnant or breastfeeding, or planning to conceive within the 3-month study duration period
• Subject has clinically significant abnormalities based on the subject's medical history, physical examination, or screening laboratory studies (as described in Appendix 1 of the Multicenter protocol). NOTE: Lab studies will only be collected in Panel A, the dose escalating portion of the study
• Subject has recent history (within the past 5 years) or current evidence of drug or alcohol abuse
• Subject has a major psychiatric illness, including any history of schizophrenia or severe psychosis, bipolar disorder requiring therapy, or any subject with suicidal ideation within the previous 3 years
• Subject is legally or mentally incapacitated
• Subject has participated in another clinical study in the past 4 weeks, or plans to participate in a treatment-based study or study in which an invasive procedure is to be performed while enrolled in this study. NOTE: Participation in a safety surveillance study is acceptable
• Subject has a history of any condition which, in the opinion of the investigator, may pose an additional risk for the subject or confound the results of the study

Following vaccination, all subjects in this study were followed for all clinical adverse experiences for 14 days postvaccination, and for vaccine-related serious adverse experiences and deaths for 84 days postvaccination (entire duration of the study).

Specific systemic AEs: fatigue, headache, myalgia, and nausea for 14 days (D) postvaccination (PV). Injection-site AEs including maximum intensity/size for 5D PV. Elevated body temperatures for 5D PV. Subjects in Panel A (N=36) were actively followed for laboratory (lab) AEs for 7D PV. Any lab abnormalities at D7 PV were followed until resolution.