Prior to the introduction of rotavirus vaccine in 2006, rotavirus was the most common cause of severe diarrhea in infants and young children in the U.S. Worldwide, rotavirus continues to be a major cause of childhood deaths. Rotavirus can cause children to lose body fluids very quickly and is especially dangerous for children less than two years of age. Children between 3 and 35 months of age have the highest risk for getting the infection. Even in the vaccine era, rotavirus causes seasonal cases of gastroenteritis from November to May each year.
Infants need three doses of rotavirus vaccine by 6 months old.
Vaccines and Preventable Diseases (CDC)