Study of Two Investigational Pneumococcal Vaccines in Healthy Adults

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.