Immunogenicity and Safety of a Booster Dose of Pneumo 23® in 12 to 18 Months-Old Children Primed With Prevnar

Inclusion Criteria: * Aged 12 to 18 months on the day of inclusion * Informed consent form signed by the parent/legally acceptable representative and by an independent witness if requested by local Ethics Committee regulation or/and if the parent/legally acceptable representative is illiterate * Child having completed the three-dose primary vaccination of Prevnar® in the hexavalent combined vaccine study (study A3L12). * Subjects and parent/guardian able to attend all scheduled visits and comply with all study procedures Exclusion Criteria: * Participation in another clinical study investigating a vaccine, drug, medical device, or a medical procedure in the 4 weeks preceding the study vaccination * Planned participation in another clinical study during the present study period * Known or suspected congenital or acquired immunodeficiency, immunosuppressive therapy such as long-term systemic corticosteroids therapy * Known systemic hypersensitivity to any of the vaccine components or history of a life-threatening reaction to the study vaccine or to a vaccine containing any of the same substances * Chronic illness at a stage that could interfere with study conduct or completion, in the opinion of the investigator * Receipt of blood or blood-derived products since birth that might interfere with the assessment of immune response * Receipt of any vaccine in the 4 weeks preceding the study vaccination * Planned receipt of any vaccine in the 4 weeks preceding or following study vaccination * History of seizures Known personal Human Immunodeficiency Virus (HIV), Hepatitis B (HB) antigen or Hepatitis C seropositivity * History of pneumococcal infection (confirmed either clinically, serologically or microbiologically) * Previous booster vaccination against the pneumococcal disease with either the study vaccine(s) or another vaccine * Thrombocytopenia, bleeding disorder or anticoagulants in the 3 weeks preceding inclusion contraindicating IM vaccination * Febrile illness (temperature ≥ 38°C) or moderate or severe acute illness/infection on the day of vaccination, according to investigator judgment.