How does the inactivated poliovirus vaccine differ from the oral poliovirus vaccine?

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Polio vaccine — polio A health care worker giving a polio vaccine to a child in Katsina state, Nigeria, 2014.

The inactivated poliovirus vaccine (IPV) and the oral poliovirus vaccine (OPV) differ primarily in their composition, administration, and immune response.1

Inactivated Poliovirus Vaccine (IPV)

Also known as the Salk vaccine, IPV is composed of killed (inactivated) poliovirus serotypes 1, 2, and 3. It is administered by injection and circulates through the bloodstream to generate antibodies that provide systemic immune memory.1

Oral Poliovirus Vaccine (OPV)

The Sabin vaccine consists of live but weakened (attenuated) poliovirus. It is administered as oral drops and replicates in the small intestine, stimulating both local and systemic immune responses. Because the virus is shed in feces, OPV can indirectly immunize others through the fecal-oral route.1

Key Considerations

While OPV is highly effective, it carries a rare risk of causing vaccine-associated paralytic polio (VAPP) or circulating vaccine-derived polioviruses (cVDPVs) due to potential mutations of the attenuated virus. Consequently, many countries, including the United States, have transitioned to using IPV to eliminate these risks while maintaining protection against the disease.1