B. IPV

Yes. When polio immunization is indicated, IPV is used for both adults and infants in the U.S., although the preparations and dose are different for these groups. For the immunization of infants, primary immunization with IPV is given at 2, 4, and 6-18 months. Then, a booster vaccine is given at 4-6 years of age.

From 1961 to 2000, OPV was the preferred vaccine for infants. It was also used as a booster for previously-immunized adults, but it was contraindicated in non-immune adults because of a risk of paralytic polio associated with the vaccine itself.

The reasons for these changes will become apparent in subsequent screens.