Vaccine associated paralytic poliomyelitis is defined as those cases of acute flaccid paralysis:
**Core Concept**
Vaccine-associated paralytic poliomyelitis (VAPP) is a rare complication of oral poliovirus vaccine (OPV) administration, where the live, attenuated virus in the vaccine can cause poliomyelitis in the recipient. This phenomenon is due to the reversion of the attenuated virus to a virulent form, leading to paralysis in some cases.
**Why the Correct Answer is Right**
VAPP occurs when the attenuated poliovirus in the OPV strain undergoes mutations, resulting in the re-emergence of neurovirulence. This is often due to the loss of mutations that attenuated the virus in the first place. As a result, the re-emergent virus can cause poliomyelitis, manifesting as acute flaccid paralysis (AFP).
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect, as vaccine-associated poliomyelitis is a specific type of AFP, whereas AFP can be caused by various factors, including non-polio enteroviruses and other conditions.
**Option B:** Incorrect, as vaccine-associated poliomyelitis is not the same as vaccine-induced poliomyelitis, which is a misnomer and not a recognized medical term.
**Option C:** Incorrect, as vaccine-associated poliomyelitis is a distinct entity from wild poliovirus-associated poliomyelitis, which is caused by the natural virus.
**Clinical Pearl / High-Yield Fact**
It's essential to note that VAPP is extremely rare, with an estimated incidence of 1 case per 2.4 million doses of OPV administered. However, the risk of VAPP is higher in areas where polio is endemic, and in individuals with weakened immune systems.
**Correct Answer:** A. Those cases of acute flaccid paralysis that are caused by the re-emergent, virulent form of the poliovirus after OPV administration.