Rotavirus is a virus that causes severe diarrhea, vomiting, and fever in infants and children. It is frequently a cause of ER visits and hospital admissions due to dehydration. It is a leading cause of death in some third world countries. It is most common during the winter months (November through April). Rotavirus Vaccine (RV) is an oral liquid vaccine that became available in 2006. An older version of this vaccine (Rotashield) was used briefly in 1998 and was taken off the market due to a rare complication. Rotateq is not associated with this rare complication (intussusception). Rotavirus vaccine is recommended at ages 2, 4, and 6 months. Side effects are mild and may include mild diarrhea or vomiting within 7 days after administration.