Which statement correctly describes VAPP and cVDPV?

• A. VAPP can occur only in the vaccinated person, not contacts.
• B. cVDPV cannot cause outbreaks and remains contained.
• C. VAPP is caused by reversion of Sabin vaccine strains; cVDPV describes outbreaks caused by vaccine-derived strains in under-immunized populations.
• D. Both VAPP and cVDPV are forms of wild poliovirus infection.

Answer: (C)

VAPP is a vaccine-related paralytic illness caused by reversion of the Sabin vaccine strains in the oral polio vaccine; it can affect the vaccinated person or contacts who are exposed to the attenuated virus. cVDPV, on the other hand, refers to outbreaks caused by vaccine-derived poliovirus strains that have mutated and regained neurovirulence, spreading in under-immunized populations. Therefore, the statement that VAPP results from reversion of Sabin strains and that cVDPV describes outbreaks caused by vaccine-derived strains in under-immunized groups is correct. VAPP can occur in contacts, and cVDPV can and does cause outbreaks in communities with low immunization coverage; these are not infections from wild poliovirus. Moreover, these issues are specific to live attenuated vaccines like OPV, whereas IPV does not cause VAPP or cVDPV.