The purpose of this study is to understand how a probiotic might change the immune response of healthy infants.

PROBLEM OF INTEREST: Lactic acid bacteria known as probiotics have been given to children and adults to prevent and treat gastrointestinal infections and to maintain intestinal health. This pilot study will collect information (biomarkers) of inflammation and immune response from healthy infants.

HOW THE PROBLEM WILL BE STUDIED: The investigators will give an active Lactobacillus-containing probiotic or an inactive placebo without Lactobacillus to 38 healthy infants in the metropolitan Atlanta area from 2 weeks before until 2 weeks after they complete their rotavirus vaccine series. Half will be assigned to receive the active probiotic, half to receive the placebo. Neither the investigators nor the parent/ guardian of the study subject will know whether their infant is receiving the probiotic or placebo. A teaspoon of blood and a stool sample will be collected from each infant before they start taking the active probiotic or placebo and 2 weeks after they complete their rotavirus vaccine series. Each infant will receive the probiotic or placebo product for 2 weeks before starting their rotavirus vaccine series until 2 weeks after they complete their rotavirus vaccine series. The blood and stool samples will be examined for levels of inflammatory markers and measures of immune response. The stool samples may be stored for the later study of probiotic bacteria as well as for other bacteria and viruses. These results will help to determine if this Lactobacillus containing probiotic has an effect on immune response and inflammation in healthy infants.

HOW RESEARCH WILL ADVANCE SCIENTIFIC KNOWLEDGE AND HUMAN HEALTH: This study will provide new information about the impact of giving a Lactobacillus-containing probiotic supplement to healthy infants. CURRENT STANDARD OF CARE: The current standard of care is for infants to receive a probiotic at the discretion of their caregiver. By studying probiotic administration in a controlled way with a fixed dose schedule and a well categorized probiotic, and measuring blood and stool markers, the investigators hope to better understand the impact of a probiotic on immune response and inflammation.

Inclusion Criteria:

• Healthy infant
• Eligible for rotavirus immunization series
• No recognized immunodeficiency
• Ability to comply with study procedures

Exclusion Criteria:

• Ineligible for rotavirus immunization series
• Recognized immunodeficiency
• Inability to comply with study procedures