This study is designed to evaluate the safety, tolerability, and immunogenicity of two investigational pneumococcal vaccines at three dose levels in healthy adults.

Primary Objective:

- To evaluate the safety and tolerability of two investigational pneumococcal vaccines.

Observational Objective:

- To evaluate the immunogenicity of the investigational pneumococcal vaccines.

An initial cohort of 6 participants will receive a single dose of one of two investigational pneumococcal vaccines. After safety evaluation of that cohort, additional cohorts will receive 2 injections 30 days apart of same investigational pneumococcal vaccine at same or increased 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:

• Known 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, or 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(s) 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
• Planned receipt of any vaccine in the 4 weeks following the trial vaccination
• Known seropositivity for Human Immunodeficiency Virus (HIV), Hepatitis B or Hepatitis C
• Laboratory confirmed / self-reported thrombocytopenia contraindicating intramuscular 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.