What it prevents: Rotavirus causes fever, diarrhea, extreme vomiting and, in severe cases, can lead to serious dehydration. Before the introduction of this vaccine in 1999, most children were infected with rotavirus before they turned three (it’s highly contagious); 1 in 150 were hospitalized because of the infection.

When it’s given: There are two different brands of oral Rotavirus vaccine. RotaTeq is given in three doses: 2 months, 4 months, and 6 months.  Rotarix is given in two doses: at 2 months and 4 months. In 2010, the FDA recommended that doctors temporarily stop using Rotarix in order for more studies to be done on it. However, if your child has had this vaccine, don’t fret; no children appear to have gotten sick from Rotarix.

Rotavirus is recommended for all full-term babies. Because it hasn't been well-studied in children born earlier than 37 weeks, your doctor will help you decide if your preemie should receive the immunization. More studies are also needed to determine its effectiveness in older babies, so it's currently only approved for use in babies 6 to 24 weeks.

What you may have heard: There’s no evidence that links the rotavirus vaccine to intussusception, a dangerous collapse of the intestines. An earlier form of the vaccine, RotaShield, did increase the risk of this serious condition but is no longer on the market.

Risk of a reaction: It’s possible that a baby may occasionally suffer from mild stomach upset (including diarrhea and vomiting) within a week of getting the vaccine. Any reaction should be mild and temporary.