What it prevents: Hepatitis A is a virus that affects the liver and can cause flu-like symptoms, jaundice (a yellowing of the eyes and skin), and death. Children, however, often don’t show any symptoms. This highly-contagious virus is spread through contact with contaminated stool or blood; it also can contaminate drinking water or food.

When it’s given: Hepatitis A is given in two doses, six months apart, between 12 and 23 months. Hep A can be given alone or as part of a combination shot with Hep B.

What you may have heard: Hepatitis A outbreaks often occur in a community through contaminated food. In recent years, there have been outbreaks in the US stemming from strawberries and green onions in several states. More recently, in 2009, there was a hepatitis A outbreak related to a national fast food chain in Illinois.

Risk of a reaction: Side effects of the vaccine are considered mild. 1 in 6 will experience soreness at the injection site, 1 in 25 will get a headache and 1 in 12 will have a decreased appetite. While very rare, it’s possible to have an allergic reaction to a component of the hepatitis A vaccine.