What it prevents: Before the IPV vaccine became available in the 1950s, as many as 20,000 people (mostly children) were paralyzed by polio, an infection of the central nervous system, in the US each year; an additional 1,000 people (again, mostly children) died from it. Polio is a highly contagious virus that can be spread through infected saliva or stool, and most people who have it don’t show any symptoms. Only a small percentage of people who get polio will become paralyzed (which shows you how widespread it was pre-vaccine to cause paralysis in so many people). Polio has been eradicated from the United States, though it still occurs elsewhere in the world. 

When it’s given: Inactivated poliovirus IPV is given in four does: 2 months, 4 months, 6 to 18 months, and a booster shot at 4 to 6 years. The shot can be part of a combination shot.

What you may have heard: You may have heard that the polio vaccine can cause polio, but it is impossible for the vaccine now given in the United States – inactivated polio virus (IPV) – to give a person polio. What is true: Oral polio virus (OPV), an older form of the vaccine that’s used in some countries where polio is still a threat because it can be more effective in a community where polio is still common, can in extremely rare cases (we’re talking 1 in 2.4 million people) cause polio; it usually occurs in someone with a weakened immune system.

Risk of a reaction: A child that’s allergic to certain antibiotics (streptomycin, polymycin, or neomycin) should not receive the vaccine. If you have a family history of these or other allergies, be sure to let your doctor know. There are no known side effects to IPV other than the mild reaction of redness or soreness at the injection site.