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

This is a Phase 3b study. Three doses of Infanrix® hexa will be administered to all subjects at the discretion of the investigator.

One complimentary dose of Rotarix will be administered to all infants enrolled in this study (both study groups) who are aged less than 6 months at Visit 3 (Week 13) as a benefit to the placebo group for participation in the study.

The study will be conducted in a double-blind manner with respect to Rotarix and placebo administered at Visit 1 and Visit 2. The parents/guardians of the subjects will know that within each pair of twins, one subject will receive the Rotarix vaccine and one subject will receive the placebo.

The study will be open label with respect to administration of the Rotarix vaccine dose given at Visit 3 to all subjects in each group who are aged less than 6 months.

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.