Rotavirus is a diarrhea-producing virus that mostly affects infants and leads to copious watery diarrhea. In the United States, because of good medical care, children almost never die from this illness. However, they often become dehydrated and are occasionally hospitalized. In 1998, an effective vaccine that decreased the severity of the illness as well as the number of hospitalizations it causes was approved after the normal review process.
But within several months of the introduction of the new vaccine, an increase in a rare bowel problem called intussusception was noted in children who had received the vaccine. The absolute increase in risk was only one in ten thousand children. However, given the fact that intussusceptions are life-threatening and sometimes require surgery, even that small an increase in the risk was enough to cause the CDC to pull the vaccine from the market in the United States.
Notice, however, that the analysis of the rotavirus vaccine depends almost entirely on the geographic location of each child. In the United States, where children rarely die of dehydration from diarrhea, the increased risk of intussusception far outweighs any concerns when compared with those associated with diarrhea.
However, outside the United States, over four hundred thousand children a year die from rotaviral diarrhea. For children in many countries, the risk of death from rotavirus far outweighs the risk of intussusception. If the vaccine was widely used in those countries, for every one child who dies from an intussusception, twenty or thirty children who otherwise would have died from the virus would now live because of the vaccine.
Of note, a different version of rotavirus vaccine was approved in 2006. So far it has the same benefits of the previous vaccine (decreased severity of illness and fewer hospitalizations), with no increased risk of intussusception. Given the history of the previous rotavirus vaccine and intussception, this new vaccine is being closely monitored.