The rotavirus vaccine is an oral vaccine that protects infants from rotavirus, which causes severe diarrhea, vomiting, and dehydration. Usage: It is given as liquid drops directly into the baby's mouth. Dosage Schedule: It is administered in either 2 doses (at 2 and 4 months) or 3 doses (at 2, 4, and 6 months), depending on the vaccine type. The series must be completed by 8 months of age. Side Effects: Most babies have no issues. Mild, temporary side effects include irritability, mild diarrhea, or vomiting. A rare bowel blockage called intussusception is extremely uncommon. Contact your pediatrician if your baby develops persistent abdominal pain.