This study aims to test the clinical samples (stool and serum) previously collected during clinical development of HRV vaccine, to identify if there is any evidence of PCV-1 replication and/or immune response to the PCV-1 in vaccinated infants.

Serum and stool samples collected from 4 clinical trials previously conducted for HRV vaccine (Rotarix™) are used in this study.

Inclusion criteria:

• Subjects enrolled previously in randomized, double-blind and placebo-controlled studies 444563/022 (NCT00263666), 444563/033 (NCT00757770), 103477 (NCT00169455), and 104480 (NCT00137930);
• Infants aged 6 to 12 weeks at Dose 1 vaccinated with either HRV vaccine or placebo;
• Infants for whom sufficient residual volume of the stool samples at predetermined time points is available;
• Infants for whom sufficient residual volume of the pre and post vaccination blood samples is available.

Exclusion criteria:

- Not applicable

Infants aged 6 to 12 weeks from 4 previously conducted clinical trials, who received 2 or 3 doses of either Rotarix™ or Placebo