This study is designed to evaluate the safety, tolerability, and immunogenicity of an investigational pneumococcal vaccine in healthy adult volunteers.

Primary Objective:

• To evaluate the safety and tolerability of an investigational pneumococcal vaccine.

Observational Objective:

• To evaluate the immunogenicity of an investigational Pneumococcal vaccine.

An initial cohort of 10 participants will receive a single dose of investigational pneumococcal vaccine. After safety assessment of this cohort during a 24-hour in-unit observation period, additional cohorts will receive two injections of the study vaccine 30 days apart, at three dose levels, in ascending doses by cohort, pending safety review at each dose level. All participants will be monitored for safety for 30 days after each vaccination.

Inclusion Criteria:

• Aged 18 to 50 years on the day of inclusion
• Informed consent form has been signed and dated
• Able to attend all scheduled visits and comply with all trial procedures
• Subject is healthy, as determined by medical history and physical examination
• For a woman of child-bearing potential, use of an effective method of contraception or abstinence from at least 4 weeks prior to first vaccination until 4 weeks after the last vaccination.

Exclusion Criteria:

• History of anaphylactic reaction or asthma
• Unknown pregnancy or positive serum/urine pregnancy test
• Currently breastfeeding a child
• Chronic illness, that in the opinion of the investigator, is at a stage that could interfere with trial conduct or completion
• Participation in another clinical trial investigating a vaccine, drug, medical device, or a medical procedure in the 4 weeks preceding the first trial vaccination
• Planned participation in another clinical trial during the present trial period
• Known or suspected congenital or acquired immunodeficiency, receipt of immunosuppressive therapy such as anti-cancer chemotherapy or radiation therapy within the preceding 6 months; or long-term systemic corticosteroid therapy (prednisone or equivalent for more than 2 consecutive weeks within the past 3 months)
• Known systemic hypersensitivity to any of the vaccine components or history of a life-threatening reaction to the trial vaccine or to a vaccine containing any of the same substances
• Current alcohol abuse or drug addiction that may interfere with the subject's ability to comply with trial procedures
• Receipt of blood or blood-derived products in the past 3 months, that might interfere with the assessment of immune response
• Receipt of any vaccine in the 4 weeks preceding the first trial vaccination, except for pandemic influenza vaccination which may be received at least two weeks before the study vaccines
• Planned receipt of any vaccine in the 4 weeks following the trial vaccination, except for pandemic influenza vaccination in the event of a local or national immunization program
• Known seropositivity for Human Immunodeficiency Virus (HIV), Hepatitis B, or Hepatitis C
• Laboratory confirmed/self-reported thrombocytopenia contraindicating intramuscular (IM) vaccination
• Deprived of freedom by an administrative or court order, or in an emergency setting, or hospitalized involuntarily
• Identified as a study site employee who is involved in the protocol and may have direct access to trial-related data
• Previous vaccination against pneumococcal disease (in the previous 5 years)
• History of pneumococcal infection (confirmed either clinically, serologically, or microbiologically) within 5 years
• At high risk for pneumococcal infection during the trial
• Living in a household with children <5 years of age.