A Study to Explore the Existence of Horizontal Transmission of the RIX4414 Vaccine Strain Between Twins Within a Family.

Inclusion Criteria:

• Subjects with a live twin living in the same household who is also enrolled in this study.
• Born after a gestation period of ≥32 weeks,
• Discharged from hospital neonatal care stay,
• Subjects who the investigator believes that their parents/guardians can and will comply with the requirements of the protocol should be enrolled in the study.
• A male or female between, and including, 6 and 14 weeks of age at the time of the first study vaccination.
• Healthy subjects as established by medical history and clinical examination before entering into the study.
• Written informed consent obtained from the parent or guardian of the subjects.

Exclusion Criteria:

• Use of any investigational or non-registered product (drug or vaccine) other than the study vaccine(s) within 30 days preceding the first dose of study vaccine, or planned use during the study period.
• Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination (no laboratory testing required).
• Any clinically significant history of chronic gastrointestinal disease.
• History of allergic disease or reactions likely to be exacerbated by any component of the vaccine.
• Acute disease at time of enrolment.
• Administration of immunoglobulins and/or any blood products since birth or planned administration during the study period.
• Contact with an immunosuppressed individual.
• Concurrently participating in another clinical study, at any time during the study period, in which the subject has been or will be exposed to an investigational or a non-investigational product (pharmaceutical product or device).
• Chronic administration of immunosuppressants since birth.
• Gastroenteritis within 7 days preceding the first study vaccine administration.
• Documented HIV-positive subject.