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.

Meningococcal disease is a serious bacterial illness. It is a leading cause of bacterial meningitis in children 2 through 18 years old in the United States. Meningitis is an infection of the covering of the brain and the spinal cord.

Pneumococcal disease refers to any illness caused by pneumococcal bacteria. These bacteria can cause many types of illnesses, including pneumonia, which is an infection of the lungs. Anyone can get pneumococcal disease, but children under 2 years old, people with certain medical conditions or other risk

Vaccination can protect older adults (and some children and younger adults) from pneumococcal disease.

Polio (or poliomyelitis) is a disabling and life-threatening disease caused by poliovirus, which can infect a person’s spinal cord, leading to paralysis. Polio vaccine can prevent polio.