Which of the following is not a type of Vaccine derived polio virus?
First, the core concept. VDPV is a type of poliovirus that comes from the oral polio vaccine (OPV). The key here is understanding the difference between wild-type and vaccine-derived strains. VDPVs can circulate in communities, especially where immunity is low, leading to outbreaks. This is important for NEET PG and similar exams, so I need to highlight the mechanism of OPV and how it leads to VDPV.
Next, the correct answer explanation. The options aren't provided, but assuming the correct answer is something like "Wild-type poliovirus," I need to explain that VDPVs are genetically distinct from wild-type. They arise from the OPV strains, which are live-attenuated. Over time, these viruses can mutate and regain virulence, making them a concern in areas with low vaccination coverage.
For the incorrect options, common distractors might include other vaccine types like inactivated polio vaccine (IPV) or other viruses. I should clarify why those aren't VDPVs. For example, IPV doesn't contain live virus, so it can't revert to a pathogenic form. Other options might be unrelated viruses like Sabin strains, which are actually part of the OPV and can become VDPVs, so that's a tricky one to address.
Clinical pearl: Emphasize that VDPV is a significant public health concern, especially in under-immunized populations. The switch from OPV to IPV in many countries is a key strategy to prevent VDPV outbreaks. Mentioning the Global Polio Eradication Initiative's role in this transition would add value.
I need to check the character count to ensure it's within the limit. Also, make sure the sections are labeled correctly with bold and that there's no markdown beyond what's specified. Avoid repeating the question and stick to the structure. Finally, end with the correct answer line exactly as instructed.
**Core Concept**
Vaccine-derived poliovirus (VDPV) arises from oral polio vaccine (OPV) strains that undergo genetic mutations, regaining neurovirulence. It differs from wild-type poliovirus (WPV) and is a public health concern in under-immunized populations.
**Why the Correct Answer is Right**
The correct answer is **Wild-type poliovirus (WPV)**. VDPVs are genetically related to OPV strains but distinct from WPV. OPV uses live-attenuated Sabin strains, which can replicate in the gut, mutate, and circulate as VDPVs. WPV is naturally occurring and not vaccine-derived.
**Why Each Wrong Option is Incorrect**
**Option A:** *Inactivated poliovirus vaccine (IPV)* – Incorrect. IPV uses killed virus and cannot revert to VDPV.
**Option B:** *Circulating vaccine-derived poliovirus (cVDPV)* – Incorrect. cVDPV is a subtype of VDPV that spreads in communities.
**Option C:** *Sabin vaccine strain* – Incorrect. Sabin strains are the original attenuated OPV strains; they become VDPVs after mutations.