By NewsDesk  @infectiousdiseasenews

Philippines health officials have reported the fourth confirmed polio (vaccine-derived poliovirus) case since September, this one from Mindanao.

Image/CDC-/ Meredith Boyter Newlove, M.S., James Archer, M.S.

The case was confirmed by the Research Institute for Tropical Medicine in Muntinlupa and the Japanese National Institute of Infectious Diseases in Tokyo.

Vaccination campaigns are scheduled for Mindanao starting November 25.

What is a vaccine-derived poliovirus?

The Global Polio Eradication Initiative says Vaccine-derived polioviruses (VDPVs) are rare strains of poliovirus that have genetically mutated from the strain contained in the oral polio vaccine.

The oral polio vaccine contains a live, attenuated (weakened) vaccine-virus. When a child is vaccinated, the weakened vaccine-virus replicates in the intestine and enters into the bloodstream, triggering a protective immune response in the child. Like wild poliovirus, the child excretes the vaccine-virus for a period of six to eight weeks. Importantly, as it is excreted, some of the vaccine-virus may no longer be the same as the original vaccine-virus as it has genetically altered during replication. This is called a vaccine-derived poliovirus.