This study aims to evaluate the serologic response to PCV-1 in the serum samples previously collected during initiation of vaccination series of Human Rotavirus (HRV) vaccine studies (1-2 months post Dose 2 of HRV vaccine or placebo). Additionally, pre-vaccination sera samples from any infants testing positive for PCV-1 antibodies at the post-vaccination time point will also be evaluated.

Serum samples collected from 6 clinical trials previously conducted for HRV vaccine (Rotarix™) are used in this study.

Inclusion Criteria:

Not applicable as no subjects will be actively enrolled in this study, only the sera samples of the subjects who were a part of previously conducted trials will be used for testing. However, the archived serum samples of only those subjects who satisfy the following criteria will be included in this study:

• Subjects who received two doses of HRV vaccine or Placebo and were included in the ATP cohort for immunogenicity in the primary studies listed.
• Subjects for whom their parents or Legally Acceptable Representatives (LARs) had agreed that their child or wards blood samples could be used for further research while giving consent for any of the primary studies listed.
• Subjects who have sufficient residual volume of serum samples at both pre- and post-vaccination time points.

Exclusion Criteria:

• Not Applicable

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