Predictors of Poor Immune Response to Rotavirus Vaccine in Infants

Infants ≤7 weeks and pregnant women will be identified through a household survey.Families of infants aged 6-7 weeks will be called to the study clinic for consenting, screening and enrollment.All enrolled subjects will be administered 2 doses of Rotarix® at 6 to 7 weeks and at 10-14 weeks of age. Other childhood vaccines will also be offered.

At enrollment, a blood specimen and breast milk specimen will be obtained from the mother and a blood, salivary and stool specimens will be obtained from the subject before administering the Rotarix® vaccine.

At the time of the 2nd administration, a breast milk specimen will be obtained from the mother and a salivary specimen will be obtained from the subject before administering the Rotarix® vaccine. At 28 days (±) 5 after the 2nd dose of Rotarix® vaccine, a blood, salivary and stool specimen will be obtained from the subject.

Whenever the family comes to the study clinic at 6-7 weeks, consent will be administered and a clinical examination conducted.If the family is willing for the mother and the child to be part of the study and the child meets the eligibility criteria, the child will be enrolled.

Depending on the group allocation the mothers will be advised to withhold or encourage breastfeeding for 30 minutes before and after receipt of Rotarix®.

subjects will be observed for 30 minutes after receipt of the vaccines to assess for immediate adverse events.

All minor illnesses that do not require hospital referral will be managed by the study physician using current practices.

All hospitalizations and deaths will be reported and reviewed by an Independent Safety Monitor.

Inclusion criteria

• At least one parent(s) or legally acceptable representative's consent for participation and are able to understand study procedures
• Subjects aged 6 to 7 weeks at recruitment
• No plans to move in the next 4 months
• Weight for age not ≤ -3 SD of WHO child growth standards

Exclusion criteria

• Infant not breastfed
• Administration of rotavirus vaccine in the past
• Known immunodeficiency disease, including HIV infection in the subject or the mother
• Known chronic enteric disease
• Diarrhea on the day of enrollment (temporary exclusion)
• Any illness requiring hospitalization (temporary exclusion)
• Any other conditions which in the judgment of the investigator warrant exclusion (e.g. no exclusion criteria but seems 'ill', investigators suspects neglect)