Nigeria was declared wild poliovirus free in August 2020, however, despite Nigeria’s wild poliovirus free status, the country is still experiencing the transmission of circulating vaccine-derived polio virus type 2 (cVDPV2). The incidences of cVDPV2 are as a result of low vaccination rates and unvaccinated children coming in contact with excretions from children who have received the live attenuated (weakened) oral polio vaccine (OPV). This is exacerbated by poor environmental sanitation as the weakened virus is mostly found in drains, ditches and soak-away pits. The government and development partners are concerned about the potentiality of ongoing cVDPV2 transmission in Nigeria and the concerns are valid as cVDPV2 has been detected in environmental samples collected in communities across several states, one of which is Kano State, which previously had a high burden of polio in Nigeria.
cVDPV2 in environmental samples in communities
In densely populated Kurnan Masallaci community in Fagge Local Government Area (LGA), Kano State, Abdullahi Umar, an environmental sample collector and his assistant Auwal Sani, stand on the small bridge over the drainage that cuts across the community, kitted up in protective gear, in preparation for sample collection. They have with them a small metal bucket tied to a rope, a small jerry can and an icebox. “This is our first sample collection this year. In 2021, some cases were recorded from samples we collected in this area”, Umar explains as he holds the jerry can ready. Sani drops the bucket into the drainage and fetches about a litre of drainage water which he pours into the jerry can, and hands the sample over to Umar who labels it and stores it in the icebox.
According to Dr. Gidado Danbatta, the World Health Organisation (WHO) local government areas (LGAs) cluster coordinator in Kano State who is witnessing the exercise, the sample will be taken to the Nigeria Centre for Disease Control (NCDC) reference laboratory in Maiduguri, Borno State for testing of cVDPV2. “We will return in two weeks to collect another sample. Mondays are our sample collection days. On Wednesday another team will collect in the other site”, Umar also adds.
Kano State has six sites where environmental samples are collected for testing of cVDPV2. According to Dr. Imam Wada Bello, Director of Disease Control at Kano State Primary Health Care Management Board, 106 cases of cVDPV2 were recorded in the state between June and December 2021, a staggering 27.5% of overall 385 cases recorded in Nigeria throughout 2021. This, he said, prompted the Outbreak Response vaccination exercise in the state.
Outbreak response to prevent outbreaks
Outbreak Response (OBR) is a vaccination exercise carried out in response to suspected or the possible spread of an infectious disease. The increase in the number of cVDPV2 cases prompted Kano State Ministry of Health, in collaboration with the National Primary Health Care Development Agency (NPHCDA) and development partners to organise three OBR schedules to ensure that all children aged 0–5 in the state receive the oral polio vaccine. OBR_0 was conducted in December 2021, OBR_1 in the second week of January 2022 and OBR_3 will be conducted in March 2022. Vaccinators are expected to go from house to house to ensure that all children under 5, regardless of whether they had been previously vaccinated, get vaccinated to protect them against the wild poliovirus.
Vaccinator, Amina Salisu, recorder, Rukayya Ibrahim and community leader representative, Umar Ahmed made up the team conducting the exercise in Charanchi community in Kumbotso LGA. According to Ibrahim, they vaccinate not less than 150 children a day, and acceptance has been high. “No house has refused to have their children vaccinated so far. We are in the second day, and we have vaccinated over 200 children already”, she said. According to Yahaya Nayaya, the Disease Surveillance and Notification Officer (DSNO) of Kumbotso LGA, the presence of the Community Leader’s representative served as an encouragement for parents to allow their children to be vaccinated. “There used to be high resistance to vaccination by parents. But with continuous sensitisation through the community leaders who have been taking part in all vaccination exercises, the story has changed. We hardly get rejected by parents now”, he added.
Back in Kurnar Masallaci, vaccinator Aisha Aminu, recorder Sadiqa Musa and community leader representative Ibrahim Ahmad are also conducting the house-to-house exercise. They are joined by Ali Chalas, the immunisation focal person in Kwaciri ward, under which Kurnar Masallaci falls. According to Chalas, even though house to house vaccination is taken seriously across the state, it is particularly personal for health workers and officials in Fagge LGA, considering the fact that cVDPV2 was detected in many of the samples taken from Kurnar Masallaci. “We are all well dedicated to this, and we will make sure every eligible child is vaccinated in our LGA”, he said.
The battle is not over
Kano State, and indeed Nigeria, has come a long way in the fight against wild poliovirus, but as long as cVDPV2 cases are still being reported, the battle is still on. cVDPV2 can emerge in settings with low population immunity and cause paralysis. The large number of cases being recorded in Kano State is proof that the state is still vulnerable. While OBR could help capture unvaccinated children and ultimately build herd immunity, Kano State needs to improve efforts to strengthen its Routine Immunisation (RI), especially the Inactivated Polio Vaccine (IPV) component. At 45.7% according to the 2018 National Demographic Health Survey, the IPV coverage should be higher, and evidence that the state must work hard to push up vaccine coverage rates, especially to curb cVDPV2 transmission.
In addition, the state needs to further strengthen its ongoing surveillance system to detect potential outbreaks of poliovirus. Six environmental sample collection sites for detecting cVDPV2 in a state with close to 20 million people and 44 LGAs coupled with its history of polio outbreaks, is inadequate. Many cases could be missed, and this could trigger an outbreak. The number of sample collection sites should be proportional to the population in the state and this requires sustained funding to maintain surveillance and outbreak response.
To further strengthen the commitment and response to outbreaks, innovative new tools like the novel oral polio vaccine type 2 (nOPV2) are being introduced in African countries like Nigeria affected by cVDPV2. Deployment of the novel vaccine is under Emergency Use Listing (EUL) and countries have to meet a readiness criteria in order to access the vaccine.
COVID-19 has taught us that we are only as strong as our weakest link. Other states particularly bordering states must remember that a pathogen can travel from a remote village to a major city in 36 hours, therefore, they must improve their abilities to fight back by advancing their capacity to prepare, detect and respond to public health emergencies.
We commend the efforts of the state government, development partners and frontline health workers in detecting and responding to cVDPV2. But more still needs to be done to sustain the gains made in the eradication of wild poliovirus, ensuring that Kano State and indeed Nigeria, maintains its polio-free status.