Marycelin Mandu Baba

Background: Sustaining progress toward polio eradication requires not only effective vaccination but also a resilient laboratory network capable of timely poliovirus detection, confirmation, and genetic characterization. In the WHO African region, the African polio laboratory network provides essential virological support for eradication efforts; however, persistent circulating Vaccine-derived Polioviruses (cVDPVs) outbreaks and increasing demands of genomic surveillance continue to challenge laboratory capacity. Despite its critical role, evidence describing the operational performance, adaptive capacity, and evolution of regional polio laboratory network remains limited. This study evaluates the performance and operational experience of the African polio laboratory network in 2025, highlighting contributions to poliovirus detection, genomic surveillance, quality assurance, and outbreak response, while sharing lessons to inform regional public health systems. Methods: A retrospective secondary data analysis was conducted using laboratory surveillance and outbreak databases, supplemented by reviews of programmatic reports. Data were cleaned and harmonized prior to analysis. Descriptive analyses were performed to assess laboratory workload, timeliness indicators, genomic capacity, quality assurance performance, and operational challenges. Qualitative review of programmatic documents was conducted to identify contextual factors influencing performance. Results: In 2025, 77,230 Acute Flaccid Paralysis (AFP) specimens were analyzed across 16 laboratories. Ninety-two percent of specimens met the timeliness target for virus isolation, and 94% met the target for PCR-ITD. Genomic sequencing confirmed 20 cVDPV outbreaks in 10 countries. The establishment of new sequencing laboratories in Uganda and Nigeria reduced turnaround times, and a 2025 expansion plan aimed to build sequencing capacity in 12 additional countries. All laboratories assessed in 2024 for virus isolation, PCR-ITD, and environmental surveillance exceeded quality assurance accreditation thresholds and were rated “Pass”. The pilot implementation of Direct Detection Nanopore Sequencing (DDNS) techniques is expected to further strengthen genomic surveillance. Challenges remain, including stock out of essential supplies, uneven workloads, and infrastructure gaps. Conclusions: The African polio laboratory network has demonstrated sustained capacity, adaptability, and innovation in supporting polio eradication activities in the WHO African region. This study provides evidence on the importance of strengthening laboratory systems, expanding genomic capacity, and maintaining quality assurance mechanisms to support the final phase of polio eradication and broader public health surveillance.

Background: This study monitored the viral content of the Novel Oral Polio Vaccine Type 2 (nOPV2) and VVM degradation during storage at different temperatures over a specified period. Method: Weekly vaccine titers were obtained until the vaccine vial monitor (VVM) degraded to 100%, except when stored in a refrigerator. Results: At refrigerator temperature, 90% and 10% of the vaccine vials retained potency for six and seven months, respectively, but none retained potency at 8 to 9 months. The median survival time was approximately seven months. The VVM remained at 0% degradation up to 4 months and changed to 5%, 10%, 20%, 30%, and 40% after 5, 6,7,8 and nine months, respectively. At room temperature, the nOPV2 retained potency during the first two weeks, declined by the third week, and none retained potency by the fourth week. The degradation of the VVM was rated 10 %, 30%, 60%, and 100% after one, two, three, and four weeks of storage, respectively. The median survival time at incubator temperature was one week, during which 10% and 90% of the vaccine in batches 2 and 1, respectively, survived, but all vials reached 0.0% at week 3. At atmospheric temperature, the survival probability was zero within a week of exposure. Time accounted for over 80% of the variation in vaccine titer. Conclusion: The potency of the nOPV2 was preserved under refrigeration for seven months, at room temperature for two weeks, in an incubator for a week, and severely degraded at atmospheric temperatures within a week.

Vaccines are biological products designed to stimulate the body’s immune system to recognize and defend against specific pathogens without causing the disease itself.1 Typically, vaccines contain w...

A fundamental question in the global commitment to polio eradication is how long a period of absence would be consistent with regional elimination, and the safe withdrawal of the oral polio vaccine is contingent on the answer. We present a statistical framework to model the time-varying sensitivity of two key components of polio surveillance - environmental sampling and clinical cases of acute flaccid paralysis - for detecting infection on a monthly basis at the local government authority level. We use this to estimate the probability of freedom from infection (FFI) at a critical prevalence level that is consistent with interruption of transmission, given the absence of virus in collected samples. We validated this framework against two periods of poliovirus absence in Nigeria (2014–2016 and 2016–2020). Our model highlights substantial heterogeneity in surveillance sensitivity over time and space and, given this, concluded an 85% probability (95% uncertainty interval: 77.1-90.0%) of the country being free from WPV1 infection after 23 months without detection from July 2014. Detection of WPV1 in July 2016 demonstrated that circulation had indeed persisted during this time. In contrast, we conclude a probability of 98% (97.5-98.5%) by the time elimination of the serotype was officially declared in 2020. The inferred probability of FFI during both time periods was found to be consistent with the retrospectively known status of regional elimination. This supports the validity of applying this framework prospectively to inform the certification of wild poliovirus elimination from remaining endemic regions, and to determine the resolution of cVDPV2 outbreaks.

Background: Poor storage of the polio vaccine in areas of inadequate or absent power to sustain the cold chain can compromise its potency. This study assessed the sustainability of the bOPV vaccine potency using viral titer and the colour of the vaccine vial monitor (VVM) when stored in the refrigerator, room, incubators, and at atmospheric temperatures over time. Method: The standardized World Health Organization (WHO) protocol was used to determine the vaccine titers weekly until the VVM degraded to 100%. Weekly average temperatures of the vaccine storage conditions were also obtained. Results: The fifty vials of bOPV tested before exposure had titers above the WHO minimum values, and VVM rated at 0% degradation. Eight of ten vials of bOPV stored in the refrigerator sustained potency for six months, with the color of VVM at 0% and 10% in five and six months, respectively. At room temperature, nine of ten vaccine vials retained potency up to three weeks, and the VVM degradation rates were 10 %, 20%, 40% and 100% after one, two, three, and four weeks, respectively. The potency of twenty vials of bOPV in the incubator was sustained for a week, and the VVM degraded by 10%, 50% and 100 % at one, two, and three weeks, respectively. At atmospheric temperature, the titers significantly dropped, and the VVM was at 100% degradation within a week. Conclusion: The potency of bOPV was most preserved under refrigeration, moderately compromised at room temperature, and severely degraded at incubator temperatures over time.

In-utero exposure to Zika virus (ZIKV) could lead to miscarriage, preterm birth and congenital Zika syndrome. This study aimed at estimating the burden of ZIKV and Dengue virus (DENV) infections among pregnant women in Bojude, Nigeria. A total of 200 blood samples were collected from pregnant women between February and April 2022. Using the updated CDC guidelines for the diagnosis of ZIKV infections, including ELISA and microneutralization test (MNT), we found that 16.5% of participants were positive for ZIKV IgM, 10% were positive for IgG, and 23% had nAb in their serum. Among the 46 ZIKV nAb-positive women, 52.2% and 10.9% were recent and previous ZIKV infections, respectively, while 6.5% had previous DENV infections. Although no recent DENV infection was detected, recent and previous ZIKV/DENV co-infections were 13.0% and 17.4%, respectively. Two participants had recent secondary ZIKV infections, while 39.1% had prolonged lifelong immunity. Recent ZIKV infection rates were significantly higher among sexually active females aged 20-29 years than other age groups, with the highest risk observed in the first trimester of pregnancy. In addition, the grand-multiparous women are at higher risk of ZIKV infections than other categories. Monotypic recent, secondary and past ZIKV infections, as well as DENV and ZIKV co-infections, were detected in both the asymptomatic and symptomatic pregnant women. These findings highlight that ZIKV infection is prevalent among pregnant women in Nigeria and underscore the associated risk factors, providing evidence-based information on the burden of ZIKV infections in DENV-endemic region.

A fundamental question in the global commitment to polio eradication is how long a period of absence would be consistent with regional elimination, and the safe withdrawal of the oral polio vaccine is contingent on the answer. We present a statistical framework to model the time-varying sensitivity of two key components of polio surveillance - environmental sampling and clinical cases of acute flaccid paralysis - for detecting infection on a monthly basis at the local government authority level. We use this to estimate the probability of freedom from infection (FFI) at a critical prevalence level that is consistent with interruption of transmission, given the absence of virus in collected samples. We validated this framework against two periods of poliovirus absence in Nigeria (2014-2016 and 2016-2020). Our model highlights substantial heterogeneity in surveillance sensitivity over time and space and, given this, concluded an 85% probability (95% uncertainty interval: 77.1-90.2%) of the country being free from WPV1 infection after 23 months without detection from July 2014. Detection of WPV1 in July 2016 demonstrated that circulation had indeed persisted during this time. In contrast, we conclude a probability of 98% (97.9-98.7%) by the time elimination of the serotype was officially declared in 2020. The inferred probability of FFI during both time periods was found to be consistent with the retrospectively known status of regional elimination. This supports the validity of applying this framework prospectively to inform the certification of wild poliovirus elimination from remaining endemic regions, and to determine the resolution of cVDPV2 outbreaks.

Introduction: Although environmental and human behavioral factors in countries with Zika virus (ZIKV) outbreaks are also common in Nigeria, such an outbreak has not yet been reported probably due to misdiagnosis. The atypical symptoms of malaria and ZIKV infections at the initial phase could leverage their misdiagnosis. This study randomly recruited 496 malaria-suspected patients who visited selected health institutions in Adamawa, Bauchi, and Borno states for malaria tests. These patients’ sera were analyzed for ZIKV antibodies using ELISA and plaque reduction neutralization tests (PRNT) at 90% endpoint. About 13.8% of Zika virus-neutralizing antibodies (nAb) did not cross-react with dengue, yellow fever, and West Nile viruses suggesting possible monotypic infections. However, 86% of the sera with ZIKV nAb also neutralized other related viruses at varied degrees: dengue viruses (60.7%), West Nile viruses (23.2%), yellow fever virus (7.1%) and 39.3% were co-infections with chikungunya viruses. Notably, the cross-reactions could also reflect co-infections as these viruses are also endemic in the country. The serum dilution that neutralized 90–100% ZIKV infectivity ranged from 1:8 to 1:128. Also, our findings suggest distinct protection against the ZIKV between different collection sites studied. As indicated by nAb, acute ZIKV infection was detected in 1.7% of IgM-positive patients while past infections occurred in 8.5% of IgM-negatives in the three states. In Borno State, 9.4% of IgG neutralized ZIKV denoting past infections while 13.5% were non-neutralizing IgM and IgG indicating other related virus infections. The age, gender, and occupation of the patients and ZIKV nAb were not significantly different. ZIKV nAb from samples collected within 1–7 days after the onset of symptoms was not significantly different from those of 7–10 days. A wider interval with the same techniques in this study may probably give better diagnostic outcomes. ZIKV nAb was significantly distinct among recipients and non-recipients of antibiotic/antimalaria treatments before seeking malaria tests. The inhibiting effect of these drugs on ZIKV infection progression may probably contribute to the absence of neurological disorders associated with the virus despite being endemic in the environment for several decades. Also, protection against ZIKV as marked by the nAb was different among the vaccinated and unvaccinated YF vaccine recipients. Thus, the YF vaccine may be a good alternative to the Zika vaccine in resource-constrained countries. Conclusion: The cryptic ZIKV infections underscore the need for differential diagnosis of malaria-suspected febrile patients for arboviruses, especially the Zika virus. The absence of systemic surveillance for the virus is worrisome because of its association with neurological disorders in newborns. Co-infections with other arboviruses may impact adversely on the management of these diseases individually.

Identifying the dissemination patterns and impacts of a virus of economic or health importance during a pandemic is crucial, as it informs the public on policies for containment in order to reduce the spread of the virus. In this study, we integrated genomic and travel data to investigate the emergence and spread of the SARS-CoV-2 B.1.1.318 and B.1.525 (Eta) variants of interest in Nigeria and the wider Africa region. By integrating travel data and phylogeographic reconstructions, we find that these two variants that arose during the second wave in Nigeria emerged from within Africa, with the B.1.525 from Nigeria, and then spread to other parts of the world. Data from this study show how regional connectivity of Nigeria drove the spread of these variants of interest to surrounding countries and those connected by air-traffic. Our findings demonstrate the power of genomic analysis when combined with mobility and epidemiological data to identify the drivers of transmission, as bidirectional transmission within and between African nations are grossly underestimated as seen in our import risk index estimates.