Rare polio type 2 ruins Nigeria's polio-free certification as the battle continues

The battle for the eradication of polio in Nigeria and by extension, Africa, has continued just when the West African country was close to becoming polio-free.

All plan was set for the distribution of the 50 million doses of polio vaccine stored in laboratory refrigerators all over Nigeria on Saturday, May 5, 2018, until an outbreak in three states - Jigawa, Sokoto, and Gombe - marred the scheduled plan to immunise every single one of the 49,882,036 known Nigerian children under 5 years old.

Now, Nigeria continues in her battle to completely eradicate polio and be certified polio-free with the African continent completely free of the virus.

The resurgence of extinct polio type 2

Time reports that the viral samples found in the affected northern states - Jigawa, Sokoto and Gombe States - were the vaccine-derived form of the polio virus, specifically Type 2.

Wild poliovirus originally has three types namely Type 1, Type 2 and Type 3.

While Types 2 and 3 are believed to have been vaccinated into extinction; Type 1 remains at large and is being battled by the public health officials and doctors in Nigeria. Vaccinations against Type 2 were discontinued in 2016 as a result of the perceived extinction of the polio type. This act makes it vexing that it was the same type 2 that turned up in the northern-state sewage.

The vaccines used in National Immunisation Days in Nigeria include protection against both Types 1 and 3. However, Type 3 was wiped recently wiped out of the country.

Speaking on the recent outbreak caused by Type 2, Dr. Tunji Funsho, a former cardiologist who is now the chairman of Rotary International’s Polio-Plus Committee in Nigeria said: “The vaccines might simply have been discarded when they were no longer needed. Even when a vial looks empty, there can be some traces of virus left.”

The outbreak

An outbreak of circulating Type 2 poliovirus in the Northern region of Nigeria upended the plans for routine immunization of children in the country. The outbreak has led to officials replacing the vaccines meant for the annual immunisation process with a crisis response in the affected area.

The 50 million doses used for the annual immunisation process will instead remain on ice until some time late in June 2018.

During a routine surveillance of sewage before the scheduled NID, traces of live poliovirus was detected in the northern states of Jigawa, Sokoto, and Gombe.

This means somewhere in those states at least a few children were carrying the virus. It had already passed through their bodies and into the environment.

The development led to the suspension of the NID while Bauchi state, which lies between Jigawa and Gombe, joined the radar as being likely to be contaminated.

Reacting to the outbreak, Dr. Mohammed Soghair, UNICEF’s polio field coordinator in Nigeria said: “When the geneticists sequenced the virus from Jigawa and Gombe they found they were identical. Somebody traveled from one state and shed the virus in the other, and that means it could have been shed in Bauchi too.”

Responding to the outbreak

In response to the surprising outbreak, vaccine teams scrambled to the Jigawa, Sokoto and Gombe States to administer a total of 2.4 million vaccine doses to children under the age of 5-years-old.

This move is believed, will cauterize the epidemiological wound before any cases of actual paralysis could turn up. Only when that situation is stabilized will the NID get underway.

With three types of polioviruses, there are two types of vaccine used to prevent the disease. They are the oral polio vaccine (OPV) and the injected polio vaccine (IPV).

While the OPV is easier and less expensive to administer - hence, it is used in mass-scale immunizations, the IPV is preferred in the developed world for routine childhood immunizations.

However, the OPV uses a live, weakened form of the poliovirus to confer immunity, and on extremely rare occasions, that virus can mutate and actually cause the disease while the IPV uses a killed virus to confer immunity.