Vaccine-resistant polio strain discovered

Newly identified mutations of the virus

In reality, the cause was something completely different. An international team including IRD researchers has just identified the virus responsible and sequenced its genetic material. The genetic sequence shows two mutations, unknown until now, of the proteins that form the "shell" (capsid) of the virus. On the face of it, this evolution complicates the task for the antibodies produced by the immune system of the vaccinated patient as they can no longer recognize the viral strain.

The researchers then tested the resistance of this variant of poliovirus on blood samples from more than 60 vaccinated people, including volunteers living in neighbouring Gabon, where part of the research team was based, and German medical students. Their antibodies were shown to be less effective against the Congo strain than against the other strains of poliovirus. The researchers estimate that 15%-30% of these people would not have been protected during the 2010 epidemic.

At a time when the global campaign to eradicate poliomyelitis is entering its final phase, researchers fear that other variants of the virus may emerge among populations immunised with the vaccine. Undoubtedly, these strains are circulating in nature. While quite rare, they could lead to fatal epidemics such as the one in 2010 in the Republic of the Congo if they reach areas where the more common strains have been eradicated, but where vaccine coverage is insufficient. The researchers are calling for better clinical and environmental monitoring to completely wipe out the scourge of polio.