_____Because the oral polio vaccine contains live attenuated viruses, mutations of these viruses can cause polio.

Verified step by step guidance

1. Understand the concept of live attenuated vaccines: These vaccines use a weakened form of the virus that is still alive but has been modified so it cannot cause disease in healthy individuals.
2. Recognize the risk of reversion: Live attenuated viruses can sometimes mutate back to a more virulent form, which can potentially cause disease.
3. Identify the mechanism of mutation: Mutations can occur during viral replication, where errors in copying the viral RNA can lead to changes in the virus's genetic material.
4. Consider the implications for vaccine-derived polio: In rare cases, these mutations can lead to vaccine-derived poliovirus (VDPV), which can cause outbreaks in under-immunized populations.
5. Explore the balance of risks and benefits: While the oral polio vaccine (OPV) is highly effective and easy to administer, the risk of mutation and VDPV is a consideration in the global strategy to eradicate polio.

Key Concepts

Live Attenuated Vaccines

Live attenuated vaccines use a weakened form of the virus that causes a disease. These vaccines stimulate a strong immune response without causing the disease itself. The oral polio vaccine (OPV) is an example, as it contains live but weakened poliovirus, which can replicate in the body and induce immunity.

Viral Mutations

Viral mutations are changes in the genetic material of a virus that can occur during replication. In the context of live attenuated vaccines, these mutations can sometimes lead to the reversion of the virus to a more virulent form, potentially causing disease. This phenomenon is particularly relevant for the OPV, where rare cases of vaccine-derived poliovirus can lead to polio outbreaks.

Vaccine-Derived Poliovirus (VDPV)

Vaccine-Derived Poliovirus (VDPV) refers to strains of poliovirus that have mutated from the live attenuated virus used in the OPV. While the vaccine is effective in preventing wild poliovirus infections, VDPVs can emerge in under-immunized populations, leading to outbreaks of polio. Understanding VDPVs is crucial for evaluating the safety and efficacy of polio vaccination strategies.