With any medicine, including vaccines, there is a chance of reactions. These are usually mild and go away on their own, but serious reactions are also possible.

Influenza (“flu”) is a contagious disease that spreads around the United States every year, usually between October and May.

Measles, mumps, and rubella are serious diseases. Before vaccines they were very common, especially among children.

Measles, mumps, rubella, and varicella are viral diseases that can have serious consequences. Before vaccines, these diseases were very common in the United States, especially among children. They are still common in many parts of the world.