The most common mild side effect is diarrhea. Children who receive the vaccine have a very slight increase (less than 5 percent) in risk of developing diarrhea. There have been no moderate or serious side effects from the vaccine.
A previous rotavirus vaccine named RotaShield was withdrawn from the market in the late 1990s, when it was found that it was associated with a very slight increase in the incidence of intussusception. Intussusception is a rare large-bowel complication in which loops of bowel collapse into each other like a telescope. This problem can occur naturally, but it occurred slightly more frequently after the RotaShield vaccine. The current vaccines are being carefully monitored for an increased rate of intussusception, and none has been found to date.