Despite being the most common cause of diarrhea in babies, rotavirus remains a relatively obscure bug for the general public. Chances are that you have never heard of this virus, yet this bug has been causing problem for hundreds of years. In 2006, a new vaccine against this virus became available, and it has already made a big impact in reducing hospitalization. However, a serious side effect tainted an older rotavirus vaccine, which was the reason the older version of this vaccine was taken off the market in 1999.