The purpose of this study is to estimate the effectiveness of 2 doses of Rotarix™ vaccination in preventing rotavirus severe gastroenteritis among children hospitalized in Belem area, Brazil.

The study will be comprised of two parts: Case-control study and Rotavirus strain surveillance.

Inclusion Criteria:

For cases:

• A male or female child born after 6 March 2006 and at least 12 weeks of age.
• Subject admitted to the study clinics/hospitals for severe gastroenteritis during the study period.
• Onset of severe gastroenteritis ≤ 14 days prior to admission.
• Laboratory confirmed rotavirus positive stool sample at hospital admission or during the first 48 hours of hospitalization.
• Written informed consent obtained from the parent or guardian of the subject.

For controls:

• Admitted for non-gastroenteritis causes at the same clinic/hospital as the case.
• Living in the same neighbourhood as the case for at least three consecutive months without any symptoms of gastroenteritis or severe gastroenteritis on the day of interview of his/ her parents/ guardians.
• Being born within +- 2 weeks from the date of birth of the case. If the number required is not available, then the range would be extended to +- 4 weeks, and ultimately up to +- 6 weeks for hospital controls. For neighbourhood controls, the range may be extended to +- 8 weeks.
• Written informed consent obtained from the parent or guardian of the child.

Exclusion Criteria:

For cases:

• Subject has previously participated as case or control in this study.
• Onset of severe gastroenteritis > 48 hours after admission to the hospital (nosocomial infections).

For controls:

• For hospital controls: Child who has symptoms of gastroenteritis during current hospitalization or on the day of interview of his/her parent or guardian or for neighbourhood controls: Child who has symptoms of gastroenteritis or severe gastroenteritis on the day of interview of his/her parent or guardian.
• Exclude children with the following vaccine preventable diseases: measles, mumps, rubella, diphtheria, pertussis, tetanus, tuberculosis, invasive Haemophilus influenzae type B (Hib) infections (meningitis, bacteraemia, septic arthritis, cellulitis, and epiglottitis) and hepatitis B.
• Child has participated in the past as a case or control in this study.
• Child living in the same house as the case

Gastroenteritis Cohort: Cases will include children born after 6 March 2006, at least 12 weeks of age and hospitalized for rotavirus severe gastroenteritis the study clinics/hospitals, during the designated study period, Hospital control cohort: Children hospitalized for non gastroenteritis causes, Neighbourhood control cohort: Children without any symptoms of gastroenteritis or severe gastroenteritis.