Dozens of polio cases have been detected in Chad just months after the UN declared the disease eradicated in Africa, but the government and World Health Organization said Friday that the infections were a vaccine-derived strain.
Sixty-six cases have been detected so far, a spokesman for the vaccination programme in Chad’s health ministry, Abdramane Adji, told AFP.
“This is no longer the poliovirus in the wild but a virus derived from the vaccine strain,” he said.
Vaccine-derived polio is a form of the illness which occurs in rare incidents when the weakened virus in the vaccine mutates.
“Ninety cases of the poliovirus derived from a vaccine strain have been reported in Chad” since September 2019, the land-locked country’s WHO representative Jean-Bosco Ndihokubwayo said.
The outbreak “only affects children who have not been vaccinated,” he added, stressing that the safety of the vaccine itself was not at issue.
The cases arose where the vaccination programme was inadequate and had left children who did not get the vaccine vulnerable to contagion from faecal matter and contaminated food.
Both the WHO and Chad’s government said the coronavirus pandemic had affected access to polio vaccinations.
On Friday the UN agency and Chad also announced two successive polio vaccination campaigns in areas with patchy health cover, to reach some three million children aged five and under.
Poliomyelitis is a disease that can attack the central nervous system and lead in the most severe cases to irreversible paralysis. It was endemic all over the world before a vaccine was developed in the 1950s.
After four years with no new cases reported, the WHO announced a “historic moment” on August 25, stating that polio had been eradicated in Africa by massive vaccination campaigns. Wild polio remains endemic only in Pakistan and Afghanistan.
The vaccine-derived poliovirus was reported in September to have affected 1,271 people worldwide since 2010, according to an AFP tally of WHO figures.
“When a population is properly immunised, it is protected against both” wild polio and the vaccine-derived kind, the WHO representative said.