Rotavirus is the most common cause of severe diarrhea among infants and young children, and is one of several viruses that cause infections often called stomach flu, despite having no relation to influenza. This ugly virus is very foul, very green, and very contagious. An oral vaccine given at two, four, and six months is effective. It’s also safer than the previous injectable vaccine, which was associated with intestinal lymph nodes leading to something called intussusception.
Taking a probiotic—an oral supplement or other preparation containing beneficial healthy bacteria to replenish the gut— seems to help reduce diarrhea associated with the rotavirus in older children and adults. To treat infants, breast-feeding moms should take the probiotic, too, as children populate their guts with bacteria found around and in their mothers’ breast milk. As that bacteria becomes popular in and on the mom, that decreases intestinal infections in your baby.
Answer excerpted from You Raising Your Child