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.
Thank you for the write-up on circulating vaccine-derived poliovirus (cVDPV), titled Strengthening Surveillance and Vaccine Uptake to Curb the Transmission of Circulating Vaccine Derived Polio Virus in Kano State. The first sentence, which reads, Nigeria was declared Polio free in August 2020, is not correct. By continuing to misrepresent what is written in the certificate issued by the ARCC, we have created the impression in the minds of Nigerians that the country is polio-free. Now that we have a surge in polio cases (caused by cVDPV2), there is not only public confusion, but also, we are finding it embarrassing and difficult to explain the current surge of polio cases in Nigeria, which stood at 397 in 2021. In fact, Nigeria has been reporting polio cases due to cVDPV for some years, prior to the wild poliovirus free declaration. We reported one case in 2016, none in 2017. We then reported thirty-four and eighteen cases in 2018 and 2019 respectively. The number of polio cases due to cVDPV in 2020, was eight, but this figure may not represent the true situation as the number of cases of 2021 jumped to three hundred and ninety-seven, a nearly fifty-fold rise in number of cases. Surveillance and immunization activities were severely hampered in 2020 and 2021, with undue focus on covid 19 to the detriment of other health interventions.
Back to the opening sentence of the article, Nigeria was declared Polio free in August 2020. This is not strictly correct. Nigeria was not declared polio-free. The words in the certificate issued by the ARCC Africa Regional Certification Commission were very specific, and in no way talked about polio-free
The certificate was titled – CERTIFICATE OF A WILD POLIOVIRUS FREE AFRICAN REGION. The details of the certificate said
We the members of the African Regional Commission for Certification of Poliovirus Eradication conclude today, Tuesday 25 August 2020, that the transmission of indigenous wild poliovirus has been interrupted in all 47 countries of the WHO Africa Region
Nowhere in that certificate is a statement that any of the 47 Africa countries, including Nigeria was declared POLIO (DISEASE) FREE. The certificate is titled CERTIFICATE OF A WILD POLIOVIRUS FREE AFRICA REGION
Home – Africa Kicks Out Wild Polio
The ARCC members could certainly not have declared Africa polio free, knowing that many African countries continued to report polio cases caused, (not by the wild poliovirus), but by circulating vaccine-derived poliovirus.
Suchard M, Tomori O, Blumberg L. Extra time, and penalties in the polio endgame. Int J Infect Dis. 2020 Feb; 91:252-254. doi: 10.1016/j.ijid.2019.12.009. Epub 2020 Jan 7. PMID: 31918002.
There is a general and persistent misinterpretation of the wordings of the certificate and a convenient elevation of the certificate to the status of a POLIO FREE CERTIFICATE
It is important that we recognize that polio cases are still occurring caused, not by WILD POLIOVIRUS, (the transmission of which has been interrupted in Africa), but by another type of poliovirus. We need to fully understand how polio cases can still occur, even after the transmission of the wild virus has been interrupted. We must understand that interrupting the transmission of indigenous wild POLIOVIRUS is not synonymous with being POLIO DISEASE free
According to WHO, wild poliovirus (WPV) is the most known form of poliovirus. However, there is another form of polio that can spread within communities: circulating vaccine-derived poliovirus, or cVDPV.
Poliomyelitis outbreaks associated with circulating vaccine-derived polioviruses (cVDPVs) have occurred in Hispaniola (2000-01), the Philippines (2001), and Madagascar (2001-02). Retrospective studies have also detected the circulation of endemic cVDPV in Egypt (1988-93) and the likely localized spread of oral poliovirus vaccine (OPV)-derived virus in Belarus (1965-66) https://pubmed.ncbi.nlm.nih.gov/15106296/
While cVDPVs are rare, they have been increasing in recent years due to low immunization rates within communities. cVDPV type 2 (cVDPV2) are the most prevalent, with 959 cases occurring globally in 2020. Nigeria reported only eight cases in 2020, but in 2021, the number of polio cases caused by cVDPV type 2 rose to three hundred and ninety- seven, almost a 50 -fold increase. Since the African Region was declared to have interrupted transmission of the indigenous wild poliovirus in August 2020, cVDPVs are now the only form of the poliovirus affecting the African Region.
https://polioeradication.org/wp-content/uploads/2018/07/GPEI-cVDPV-Fact-Sheet-20191115.pdf Home – Africa Kicks Out Wild Polio
So, how does cVDPV occur? The oral polio vaccine (OPV) which has brought the wild poliovirus to the brink of eradication has many benefits: the live attenuated (weakened) vaccine virus provides better immunity in the gut, which is where polio replicates. The vaccine virus is also excreted in the stool, and in communities with low-quality sanitation, this means that it can be spread from person to person and help protect the community. However, in communities with low immunization rates, as the virus is spread from one unvaccinated child to another over a prolonged period (often over the course of about 12-18 months), it can mutate and take on a form that can cause paralysis just like the wild poliovirus. This mutated poliovirus can then spread in communities, leading to cVDPV.
To stop the spread of cVDPVs, it is important to realize and recognize that the cause of cVDPV is low immunization rates. Therefore, the best way to prevent them and stop cVDPV outbreaks to vaccinate children and substantially increase the quality and coverage of routine immunization. The polio vaccine protects children whether the kind of polio is wild poliovirus or vaccine-derived poliovirus. Outbreaks (whether WPV or cVDPV) are usually rapidly stopped with 2–3 rounds of high-quality supplementary immunization activities (immunization campaigns). In addition to high-quality immunization campaigns, the global polio eradication programme has introduced and deployed the improved and novel oral polio vaccine type 2, or nOPV2. This vaccine is like mOPV2 (the monovalent oral polio vaccine type 2), the current outbreak response vaccine that is used when cVDPV type 2 outbreaks occur. The nOPV2 vaccine virus is less likely to mutate and cause disease in communities with low immunization rates. This will help reduce the risk of cVDPV2 outbreaks.
In November 2020, the nOPV2 vaccine was given Emergency Use Listing status by the World Health Organization (WHO). Since then, more than 80 million children have been vaccinated with the novel oral polio vaccine type 2 (nOPV2) in Nigeria and five other countries – Benin, Congo, Liberia, Niger, and Sierra Leone. Nigeria was the first country to use nOPV2 to tackle an outbreak in March 2021, vaccinating 7 million children in six states.
The ARCC declaration of Tuesday 25 August 2020, that the transmission of indigenous wild poliovirus has been interrupted in all 47 countries of the WHO Africa Region, is a battle won. We must wake up from the unsafe security of false polio disease free status. The war continues with cVDPV still causing polio disease in poorly, under vaccinated or non-vaccinated children. It is important that we recognize that unless we sustain high quality and high coverage routine immunization, our children will continue to be paralyzed by circulating vaccine-derived poliovirus.