Circulating vaccine-derived polioviruses (cVDPVs) arise from which vaccine?

• A. Inactivated polio vaccine (IPV)
• B. A combination of both
• C. Neither
• D. Oral polio vaccine (OPV)

Answer: (D)

Circulating vaccine-derived polioviruses come from the live, attenuated virus used in the oral polio vaccine. Because OPV contains a live virus, it can replicate in the gut and be shed in stool. In communities with incomplete immunization, that shed virus can spread from person to person, continuing to replicate and accumulate mutations. Some of these mutations can restore the virus’s ability to cause disease and to transmit, leading to outbreaks of poliovirus that are derived from the vaccine strain. The inactivated polio vaccine, by contrast, uses killed virus and cannot replicate or be shed, so it cannot give rise to circulating vaccine-derived strains. That’s why the source is the oral polio vaccine.