What was the main rationale for switching from OPV to IPV and for using a bivalent OPV rather than a trivalent OPV?

What was the main rationale for switching from OPV to IPV and for using a bivalent OPV rather than a trivalent OPV?

• A. To increase all three serotypes in OPV without IPV.
• B. To replace all OPV doses with IPV entirely.
• C. To eliminate OPV type 2 from the vaccine and create a bivalent OPV, while introducing IPV to protect against cVDPV2.
• D. To decrease overall vaccination coverage.

Answer: (C)

The key idea is reducing the risk posed by the live vaccine while maintaining strong protection against all polio serotypes. OPV uses live attenuated viruses for types 1, 2, and 3. After wild-type type 2 diminished, outbreaks of vaccine-derived poliovirus type 2 (VDPV2) from the type 2 component of OPV became a major problem. To prevent those VDPV2 outbreaks, the global strategy shifted to a bivalent OPV that covers only types 1 and 3, and introduced inactivated polio vaccine (IPV) to preserve immunity to type 2 without using a live type 2 vaccine. IPV contains inactivated viruses, so it cannot mutate or spread and cannot cause vaccine-derived disease, while still providing systemic protection against paralysis from type 2. At the same time, bOPV continues to induce mucosal immunity against types 1 and 3, helping to interrupt transmission of those serotypes. This combination achieves protection against all three serotypes with a lower risk of vaccine-derived outbreaks.

The key idea is reducing the risk posed by the live vaccine while maintaining strong protection against all polio serotypes. OPV uses live attenuated viruses for types 1, 2, and 3. After wild-type type 2 diminished, outbreaks of vaccine-derived poliovirus type 2 (VDPV2) from the type 2 component of OPV became a major problem. To prevent those VDPV2 outbreaks, the global strategy shifted to a bivalent OPV that covers only types 1 and 3, and introduced inactivated polio vaccine (IPV) to preserve immunity to type 2 without using a live type 2 vaccine. IPV contains inactivated viruses, so it cannot mutate or spread and cannot cause vaccine-derived disease, while still providing systemic protection against paralysis from type 2. At the same time, bOPV continues to induce mucosal immunity against types 1 and 3, helping to interrupt transmission of those serotypes. This combination achieves protection against all three serotypes with a lower risk of vaccine-derived outbreaks.