The purpose of this study is to describe the immunogenicity and safety of Sanofi Pasteur's DTaP-IPV-Hep B-PRP-T fully liquid combined hexavalent vaccine (Hexaxim®) administered at 2, 3, and 4 months of age and at 16 to 17 months of age in infants and toddlers who received a dose of Hep B vaccine at birth or within 1 week after birth.

Primary Objective:

• To describe the safety profile after each and all doses of Sanofi-Pasteur's DTaP-IPV-Hep B-PRP-T combined vaccine in Vietnamese infants and toddlers.

Secondary Objective:

• To demonstrate the non-inferiority of the immune response to all antigens induced by the study vaccine in Vietnamese infants one month after the third dose in a 3-dose primary series with the immune response to all antigens induced by the same study vaccine outside Vietnam.
• To evaluate the immunogenicity of the study vaccine one month after the 3-dose primary series.
• To describe the persistence of all antibodies before receipt of the booster vaccination.
• To evaluate the immunogenicity of the study vaccine one month after the booster.

Participants will receive a total of 5 doses of Hep B: One dose of Hep B monovalent vaccine given at birth or within 1 week after birth followed by 3 doses of the Sanofi Pasteur's hexavalent vaccine given as primary series at 2, 3, and 4 months of age and then a booster dose at 16 to 17 months of age, to comply with Vietnamese vaccination recommendations.

Inclusion Criteria:

• Aged 61 to 91 days on the day of the first study visit
• Born at full term of pregnancy (≥ 37 weeks) and with a birth weight ≥2.5 kg
• Informed consent form has been signed and dated by the parent(s) or other legally acceptable representative (and by an independent witness if required by local regulations)
• Subject and parent/legally acceptable representative are able to attend all scheduled visits and to comply with all trial procedures
• Have received one dose of Hep B vaccine at birth or within 1 week after birth (documented according to the national recommendations).

Exclusion Criteria:

• Participation in the 4 weeks preceding the first trial vaccination or planned participation during the present trial period in another clinical trial investigating a vaccine, drug, medical device, or medical procedure
• Receipt of any vaccine in the 4 weeks preceding the first trial vaccination or planned receipt of any other vaccine within the period from 8 days before to 8 days after each subsequent trial vaccination except for Bacille Calmette Guerin (BCG) vaccination (any administration of oral poliovirus vaccine (OPV) in the context of oral poliovirus vaccine-national immunization days (NIDs) does not fall within the scope of this exclusion criterion)
• Previous vaccination against diphtheria, tetanus, pertussis, poliomyelitis, hepatitis B (except the dose of Hep B vaccine given at birth or within 1 week after birth) diseases or Haemophilus influenzae type b infection with either the trial vaccine or another vaccine (any administration of OPV in the context of OPV-NIDs does not fall within the scope of this exclusion criterion)
• Past or current receipt of immune globulins, blood or blood-derived products or planned administration during the trial
• Known or suspected congenital or acquired immunodeficiency; or receipt of immunosuppressive therapy, such as anti-cancer chemotherapy or radiation therapy since birth; or long-term systemic corticosteroid therapy (prednisone or equivalent for more than 2 consecutive weeks since birth)
• History of diphtheria, tetanus, pertussis, poliomyelitis, hepatitis B, or Haemophilus influenzae type b infections (confirmed either clinically, serologically or microbiologically)
• Known personal or maternal history of Human Immunodeficiency Virus (HIV), or hepatitis C seropositivity
• Known systemic hypersensitivity to any of the vaccine components, or history of a life-threatening reaction to the vaccine used in the trial or to a vaccine containing any of the same substances
• Known thrombocytopenia, as reported by the parent/legally acceptable representative
• Bleeding disorder, or receipt of anticoagulants in the 3 weeks preceding inclusion, contraindicating intramuscular vaccination
• History of seizures
• In an emergency setting, or hospitalized involuntarily
• Chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with trial conduct or completion
• Moderate or severe acute illness/infection (according to investigator judgment) on the day of vaccination or febrile illness (temperature ≥38.0°C). A prospective subject should not be included in the study until the condition has resolved or the febrile event has subsided
• Identified as a natural or adopted child of the Investigator, relatives or employee with direct involvement in the proposed study.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org