Final answer:
The Salk polio vaccine is inactivated and currently used in the US, while the Sabin vaccine contains attenuated virus, mimics normal infection routes, and requires four doses.
Explanation:
The Salk polio vaccine: is an inactivated vaccine that is currently administered in the United States. In contrast, the Sabin polio vaccine contains an attenuated virus, is not currently administered in the United States, mimics the normal route of infection, and requires four doses for children.
Learn more about polio vaccines here:
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