What are the key features of OPV-related vaccine-derived risks, such as VAPP and cVDPV?

• A. OPV induces no immunity and has no risk of reversion.
• B. OPV cannot cause vaccine-derived strains.
• C. OPV can revert to neurovirulent forms leading to VAPP or cVDPV.
• D. OPV only protects against one serotype.

Answer: (C)

OPV uses live attenuated poliovirus strains that replicate in the gut to build immunity, but because they are live, they carry a small risk of reversion toward neurovirulence. When the vaccine virus reverts, it can cause vaccine-associated paralytic polio in the vaccinated person or in close contacts. If the reverted virus is shed and continues to circulate in a community with insufficient immunity, it can accumulate additional mutations and behave like wild poliovirus, leading to outbreaks of circulating vaccine-derived poliovirus. This is the fundamental distinction: OPV can provide strong intestinal and overall immunity and also carries the risk of reversion and transmission, which is the basis for vaccine-derived risks. The other statements mischaracterize OPV by saying there is no immunity or no risk of vaccine-derived strains, or by oversimplifying serotype protection.