The history of polio vaccination with "Sabin's OPV" 60 years after its introduction in Italy: an unforgivable "delay".

In the spring of 1964, polio vaccination with the oral vaccine developed by Albert Sabin began in Italy. Polio was feared in the world and in Italy. Thus, between 1957 and the beginning of 1958, Italian children began receiving the "Salk vaccine", though the results were not particularly convincing. In July 1960, the international scientific community was able to verify the data from the mass testing of the Sabin vaccine. It became clear that the OPV, could prevent the virus from multiplying, thereby providing greater protection and determining the eradication of the disease. In 1960 over 70 million people in the USSR alone had already received the oral vaccine and mass vaccination in the USA would start in March 1961. However, in Italy there was no similar initiative; only later the new vaccine was accepted but was not made compulsory at the beginning. As a result of the commission's report, registration of the "Polioral" vaccine, was authorized in September 1962 but the sale of the vaccine was not authorized until November 1963. At the beginning of 1964, the production of "Polioral" started and the product was marketed and on the 1 st of March 1964, anti-polio vaccination with the "Sabin anti-polio vaccine" also began in Italy. This manuscript focuses on a crucial issue about a historical delay for public health and it points out as the preparation and diffusion of the Sabin polio vaccine demonstrates that decisions regarding health treatments, and specifically vaccination campaigns, must be based exclusively on the results of clinical studies and on independent evaluation by the scientific community. This process ensures trust in vaccines, adequate protection of public health andcitizens' well-being.

Report offers harsh verdict on global polio vaccine switch.

Draft evaluation calls 2016 decision to change oral vaccines a "failure".

Exploring the path to polio eradication: insights from consecutive seroprevalence surveys among Pakistani children.

Introduction: After trivalent oral poliovirus vaccine (tOPV) cessation, Pakistan has maintained immunity to type 2 poliovirus by administering inactivated polio vaccine (IPV) in routine immunization, alongside monovalent OPV type 2 (mOPV2) and IPV in supplementary immunization activities (SIAs). This study assesses the change in poliovirus type 2 immunity after tOPV withdrawal and due to SIAs with mOPV2 and IPV among children aged 6-11 months. Methods: Three cross-sectional sequential serological surveys were conducted in 12 polio high-risk areas of Pakistan. 25 clusters from each geographical stratum were selected utilizing probability proportional to size. Results: Seroprevalence of type 2 poliovirus was 49%, with significant variation observed among surveyed areas; <30% in Pishin, >80% in Killa Abdullah, Mardan & Swabi, and Rawalpindi. SIAs with IPV improved immunity from 38 to 57% in Karachi and 60 to 88% in Khyber. SIAs with IPV following mOPV2 improved immunity from 62 to 65% in Killa Abdullah, and combined mOPV2 and IPV SIAs in Pishin improved immunity from 28 to 89%. Results also reflected that immunity rates for serotypes 1 and 3 were consistently above 90% during all three phases and across all geographical areas. Conclusion: The study findings highlight the importance of implementing effective vaccination strategies to prevent the re-emergence of poliovirus. Moreover, the results provide crucial information for policymakers working toward achieving global polio eradication.

Impact of COVID -19 on expanded programme on Immunisation in District Dir lower Khyber Pakhtunkhwa.

Objectives: To study the impact of coronavirus disease-2019 on Expanded Programme on Immunisation in a rural setting. METHODS: The descriptive, cross-sectional study was conducted in five union councils of District Dir Lower, in the Khyber Pakhtunkhwa province of Pakistan. Data was collected from March to August 2020, which was a period of lockdowns in the wake of the coronavirus disease-2019, and then from March to August 2021. The sample comprised children aged <2 years. Data was analysed using SPSS 25. RESULTS: Of the 330 children, 210(63.6%) were boys, and 120(36.4%) were girls, and all 330(100%) were located in rural areas. First-phase data showed that the maximum coverage rate of immunisation was 258(78.2%) noted in OPV1(Oral Polio Vaccine) Penta1(Pentavalent vaccine), PCV10-1 (Pneumococcal pneumonia) and Rota 1(Rota Vaccine), and the least vaccination rate was 68.2% for Measle-1. In the second phase, 23% incline was noted in Measles-2 vaccination, followed by 16.3% in OPV2, Penta 2, PCV10-2 and Rota 2, 16% in Measles-1, 14% in OPV-3, Penta-3, PCV10-3, Rota-3 and IPV, 11.5% in OPV-1, Penta-1, PCV10-1, and Rota-1, and 10.6% in OPV-0 and BCG-0. CONCLUSIONS: Immunisation programme was affected by lockdowns during the active phase of the coronavirus disease-2019 pandemic.

Monitoring the evolution of vaccine-derived poliovirus in East and Southern African countries, 2010 - 2021.

Introduction: the Africa region was certified indigenous wild poliovirus-free in August 2020. Countries in East and Southern Africa have, during acute flaccid paralysis (AFP) and environmental surveillance (ES), detected equally concerning vaccine-derived polioviruses (VDPVs) that have not been systematically documented to guide programming in the sub-region. The study documents trends and salient observations of the VDPVs by country of detection, for 11 years from 2010 to 2021. Methods: we conducted secondary data analysis, a descriptive study design, by deploying field and laboratory of AFP and environmental surveillance databases of the 20 East and Southern African countries from 2010 to 2021. Results: a total of 318 VDPVs were reported over the study period. The majority were from AFP cases (58.8%) and the rest equally distributed between healthy community children and environmental surveillance sources. More polioviruses were detected after 2016 than during the period before. We observed that more boys were affected by VDPVs compared to girls. Children under 5 years were more affected than other age groups, with a mean age of 3.6 years. Delay of samples in the field seemed to increase the likelihood of not reporting VDPVs and not mounting timely public health detailed investigations and vaccination responses. Conclusion: the study provides useful evolutional trends of VDPVs for surveillance and vaccination programming. We also noted that the VDPV2s have been increasing after the 2016 tOPV to oral polio vaccine (bOPV) switch. The COVID-19 pandemic emergence in 2020, led to a decline in AFP, ES surveillance, and immunization activities. Our findings point to the need to implement enhanced tailored childhood immunization recovery strategies and to speed up the use of inactivated polio vaccine (IPV) to boost population immunity.

High throughput AS LNA qPCR method for the detection of a specific mutation in poliovirus vaccine strains.

Sabin Inactivated Poliovirus Vaccine (sIPV) has become one of the preferred vaccination options for the last step in the Poliovirus eradication program. Sequencing of poliovirus samples is needed during the manufacturing of poliovirus vaccines to assure the safety and immunogenicity of these vaccines. Next-generation sequencing analysis is the current costly and time-consuming gold standard for monitoring the manufacturing processes. We developed a low-cost and quick, highly sensitive, and allele-specific locked nucleic acid-probe-based reverse transcription quantitative PCR alternative that can accurately detect mutations in poliovirus vaccine samples during process development, scaling up, and release. Using the frequently in vitro occurring and viral replication-impacting VP1-E295K mutation as a showcase, we show that this technology can accurately detect E295K mutations in poliovirus 2 samples to similar levels as NGS. The qPCR technology was developed employing a synthetic dsDNA fragment-based standard curve containing mixes of E295K-WT (wildtype) and Mut (mutant) synthetic dsDNA fragments ranging from 1 × 107 copies/µL to 1 × 102 copies/µL to achieve a linear correlation with R2 > 0.999, and PCR efficiencies of 95-105 %. Individual standard concentration levels achieved accuracies of ≥92 % (average 96 %) and precisions of ≤17 % (average 3.3 %) RSD. Specificity of locked nucleic acid (LNA)-probes was confirmed in the presence and absence of co-mutations in the probe-binding region. Application of the developed assay to Sabin Poliovirus type 2 production run samples, illustrated a linear relationship with an R2 of 0.994, and an average accuracy of 97.2 % of the variant (allele)-specific AS LNA qPCR result, compared to NGS. The assay showed good sensitivity for poliovirus samples, containing E295K mutation levels between 0 % and 95 % (quantification range). In conclusion, the developed AS LNA qPCR presents a valuable low-cost, and fast tool, suitable for the process development and quality control of polio vaccines.

Novel Oral Poliovirus Vaccine 2 Safety Evaluation during Nationwide Supplemental Immunization Activity, Uganda, 2022.

Given its enhanced genetic stability, novel oral poliovirus vaccine type 2 was deployed for type 2 poliovirus outbreak responses under World Health Organization Emergency Use Listing. We evaluated the safety profile of this vaccine. No safety signals were identified using a multipronged approach of passive and active surveillance.

[Eradication of poliomyelitis in Spain: What has happened in the last decade?] / Erradicación de la poliomielitis en España: ¿qué ha pasado en la última década?

On the 60th anniversary of the initiation of the polio vaccination campaign in Spain, the significant milestone in achieving disease control is highlighted. There has been a shift from an incidence of over 2,000 yearly cases in the 1960s to a sustained absence of wild poliovirus (WPV) since 1988. Despite the observed negative impact on polio vaccination coverage at the onset of the COVID-19 pandemic, these rates gradually recovered, reaching 98.2% in primary vaccination in 2022. Over the past decade, two essential elements have been identified to maintain the goal of polio elimination and that reinforces the importance of sustaining high vaccination coverage: robust epidemiological surveillance systems and a swift response to alerts to protect the vulnerable population and prevent virus reintroduction. In order to achieve eradication, it is crucial to interrupt international transmission and maintain continuous high-quality surveillance and effective coordination across different levels in response to any detection of PV, wild or vaccine derived. This article aimed to provide a comprehensive view of the polio eradication situation in Spain, focusing on the key events that occurred in the last decade and the present and future challenges.

hito en el control de la enfermedad que ha supuesto el cambio desde una incidencia de más de 2.000 casos anuales en la década de los 60 a una ausencia mantenida de poliovirus (PV) salvaje desde 1988. A pesar del impacto negativo observado en las coberturas de vacunación de poliomielitis al inicio de la pandemia de la COVID-19, estas se fueron recuperando, alcanzando un 98,2% en la primovacunación en 2022. En la última década se han identificado dos elementos esenciales para mantener el objetivo de eliminación de la poliomielitis y que, además, refuerzan la importancia de mantener altas coberturas de vacunación: los sistemas de vigilancia epidemiológica robustos y la respuesta rápida a las alertas para proteger a la población vulnerable y evitar la circulación del virus. Es crucial interrumpir la transmisión a nivel internacional para lograr la erradicación, manteniendo una vigilancia continua de alta calidad y una coordinación efectiva entre los diferentes niveles frente a cualquier detección de PV, ya sea salvaje o derivado de la vacuna. Este artículo tuvo como objetivo proporcionar una visión integral sobre la situación de erradicación de la poliomielitis en España, centrándose en los eventos clave ocurridos en la última década y en los retos presentes y futuros.

Circulating vaccine derived polio virus type 2 outbreak and response in Yemen, 2021-2022, a retrospective descriptive analysis.

BACKGROUND: The outbreaks of circulating Vaccine Derived Polio Viruses (cVDPVs) have emerged as a major challenge for the final stage of polio eradication. In Yemen, an explosive outbreak of cVDPV2 was reported from August 2021 to December 2022. This study aims to compare the patterns of cVDPV2 outbreak, response measures taken by health authorities, and impacts in southern and northern governorates. METHOD: A retrospective descriptive study of confirmed cases of VDPV2 was performed. The data related to cVDPV2 as well as stool specimens and environmental samples that were shipped to WHO-accredited labs were collected by staff of surveillance. Frequencies and percentages were used to characterize and compare the confirmed cases from the southern and northern governorates. The average delayed time as a difference in days between the date of sample collection and lab confirmation was calculated. RESULTS: The cVDPV2 was isolated from 227 AFP cases reported from 19/23 Yemeni governorates and from 83% (39/47) of environmental samples with an average of 7 months delayed from sample collection. However, the non-polio AFP (NPAFP) and adequate stool specimen rates in the north were 6.7 and 87% compared to 6.4 and 87% in the south, 86% (195) and 14%(32) out of the total 227 confirmed cases were detected from northern and southern governorates, respectively. The first and second cases of genetically linked isolates experienced paralysis onset on 30 August and 1st September 2021. They respectively were from Taiz and Marib governorates ruled by southern authorities that started vaccination campaigns as a response in February 2022. Thus, in contrast to 2021, the detected cases in 2022 from the total cases detected in the south were lower accounting for 22% (7 of 32) of compared to 79% (155 of 195) of the total cases the north. CONCLUSION: A new emerging cVDPV2 was confirmed in Yemen. The result of this study highlighted the impact of vaccination campaigns in containing the cVDPV2 outbreak. Maintaining a high level of immunization coverage and switching to nOPV2 instead of tOPV and mOPV2 in campaigns are recommended and environmental surveillance should be expanded in such a risky country.

A phase 3 randomized, open-label study evaluating the immunogenicity and safety of concomitant and staggered administration of a live, pentavalent rotavirus vaccine and an inactivated poliomyelitis vaccine in healthy infants in China.

This open-label, randomized, phase 3 study in China (V260-074; NCT04481191) evaluated the immunogenicity and safety of concomitant and staggered administration of three doses of an oral, live, pentavalent rotavirus vaccine (RV5) and three doses of an intramuscular, inactivated poliomyelitis vaccine (IPV) in 400 healthy infants. The primary objective was the non-inferiority of neutralizing antibody (nAb) responses in the concomitant- versus the staggered-use groups. Antibody responses were measured at baseline and 1-month post-dose 3 (PD3). Parents/legal guardians recorded adverse events for 30 or 15 d after study vaccinations in the concomitant-use or staggered-use groups, respectively. At PD3, >98% of participants seroconverted to all three poliovirus types, and the primary objective was met as lower bounds of the two-sided 95% CI for between-group difference in nAb seroconversion percentages ranged from - 4.3% to - 1.6%, for all poliovirus types, p < .001. At PD3, geometric mean titers (GMTs) of nAb responses to poliovirus types 1, 2, and 3 in the concomitant-use group and the staggered-use group were comparable; 100% of participants had nAb titers ≥1:8 and ≥1:64 for all poliovirus types. Anti-rotavirus serotype-specific IgA GMTs and participants with ≥3-fold rise in postvaccination titers from baseline were comparable between groups. Administration of RV5 and IPV was well tolerated with comparable safety profiles in both groups. The immunogenicity of IPV in the concomitant-use group was non-inferior to the staggered-use group and RV5 was immunogenic in both groups. No safety concerns were identified. These data support the concomitant use of RV5 and IPV in healthy Chinese infants.

Safety of incidental exposure to the novel oral poliovirus vaccine type 2 in pregnancy: A longitudinal observational study in Mozambique, 2022-2023

To minimize the risk of vaccine-derived poliovirus emergences, the novel oral poliovirus vaccine type 2 (nOPV2), was bioengineered to have increased genetic stability compared to Sabin OPV and recommended for outbreak response Emergency Use Listing by WHO. Although pregnant women are not a target population for this vaccine, a theoretical risk of incidental exposure exists via pharyngeal or faecal shedding from vaccinated children in the household or close community. Methods: This was an observational study of pregnant women conducted in Nampula (exposed cohort) and Maputo (non-exposed cohort) in Mozambique from August 2022 to June 2023. Two nOPV2 campaigns were conducted in Nampula and none in Maputo. Women were followed-up during routine prenatal consultation, delivery, and 28-day neonate visits for obstetric anomalies and pregnancy outcomes. Sociodemographic, medical, and obstetric history was captured. Results: Three hundred twenty-six pregnant women were enrolled from Nampula and 940 from Maputo City. Stillbirth prevalence (2·3% vs 1·6%, p = 0·438), low birth weight (8·9% vs 8·2%, p = 0·989), congenital anomalies (1 % vs 0·5%, p = 0·454), neonatal death (2·3% vs 1·6%, p = 0·08), and maternal death (0 % vs 0·2%, p = 0·978) did not differ amongst exposed and non-exposed cohorts. There was an increased rate of pre-term delivery in the exposed cohort (18·4% vs 11·0%, p = 0·011). Conclusion: We did not observe an increased frequency of adverse pregnancy outcomes due to passive nOPV2 exposure. A higher frequency of preterm delivery needs to be further investigated. The data reported herein support the continued use of nOPV2 for poliovirus outbreak response and full licensure of the vaccine.

Observational analysis of the immunogenicity and safety of various types of spinal muscular atrophy vaccines.

BACKGROUND: This study aimed to evaluate the immunogenicity and safety of different types of poliovirus vaccines. METHODS: A randomized, blinded, single-center, parallel-controlled design was employed, and 360 infants aged ≥ 2 months were selected as study subjects. They were randomly assigned to bOPV group (oral Sabin vaccine) and sIPV group (Sabin strain inactivated polio vaccine), with 180 infants in each group. Adverse reaction events in the vaccinated subjects were recorded. The micro-neutralization test using cell culture was conducted to determine the geometric mean titer (GMT) of neutralizing antibodies against poliovirus types I, II, and III in different groups, and the seroconversion rates were calculated. RESULTS: Both groups exhibited a 100% seropositivity rate after booster immunization. The titers of neutralizing antibodies for the three types were predominantly distributed within the range of 1:128 to 1:512. The fold increase of type I antibodies differed markedly between the two groups (P < 0.05). Moreover, the fold increase of type II and type III antibodies for poliovirus differed slightly between the two groups (P > 0.05). The fourfold increase rate in sIPV group was drastically superior to that in bOPV group (P < 0.05). When comparing the post-immunization GMT levels of type I antibodies in individuals who completed the full course of spinal muscular atrophy vaccination, bOPV group showed greatly inferior levels to sIPV group (P < 0.05). For type II and type III antibodies, individuals in bOPV group demonstrated drastically superior post-immunization GMT levels to those in sIPV group (P < 0.05). The incidence of adverse reactions between the bOPV and sIPV groups differed slightly (P > 0.05). CONCLUSION: These findings indicated that both the oral vaccine and inactivated vaccine had good safety and immunogenicity in infants aged ≥ 2 months. The sIPV group generated higher levels of neutralizing antibodies in serum, particularly evident in the post-immunization GMT levels for types II and III.

Immunogenicity and lot-to-lot consistency of booster shot with Sabin inactivated poliomyelitis vaccine in Chinese children aged 18-24 Months: A phase â £ clinical trial.

BACKGROUND: There has been no data on the immunogenicity and safety of the 4th booster dose of the sIPV immunization in 18-24 months old children in post-marketing studies of large cohort providing with robust results. METHOD: In a phase Ⅳ randomized, double-blinded clinical trial, 1200 participants aged 2 months were immunized with three consecutive doses of sIPV at 2, 3, and 4 months old to complete primary immunization. Out of the 1200 participants, 1129 received the 4th dose of sIPV as booster immunization. Immunogenicity was evaluated in 1100 participants. RESULTS: Seropositive rates of the anti-poliovirus type 1, 2, and 3 neutralizing antibodies were 99.9 %, 98.0 %, 98.2 %, respectively, with GMTs of 557.0, 146.1, 362.0 one year after primary vaccination. After booster vaccination between 18 and 24 months old, the seropositive rates for 3 types all reached 100.0 %, with GMTs of 8343.6, 5039.6, 5492.0, respectively. Particularly for the anti-poliovirus type 2 antibody, the GMT was 230.4 after primary immunization, maintained to 146.1 one year after primary immunization, and increased to as high as 5039.6 after booster vaccination. The GMT ratios between each batch groups after booster immunization were between 0.67 and 1.50, meeting the immunological equivalence criteria. The incidence rate of adverse reaction was 23.0 %, which was comparable to those in the phase Ⅲ trial but had a lower incidence. Furthermore, no SUSAR was reported in this study. INTERPRETATION: In conclusion, as the anti-poliovirus antibodies gradually waned one year post sIPV primary vaccination, especially the type 2 antibody waned to a very low level, suggesting the importance of the booster immunization for children at the age of 18-24 months old. The booster shot can greatly enhance the antibody level and protect children from the potential risk of infection with WPV and VDPV by supplementing the anti-poliovirus type 2 immunity gap in the current real world. Clinic Trial Registration. NCT04224519.

Safety of incidental exposure to the novel oral poliovirus vaccine type 2 in pregnancy: A longitudinal observational study in Mozambique, 2022-2023.

BACKGROUND: To minimize the risk of vaccine-derived poliovirus emergences, the novel oral poliovirus vaccine type 2 (nOPV2), was bioengineered to have increased genetic stability compared to Sabin OPV and recommended for outbreak response Emergency Use Listing by WHO. Although pregnant women are not a target population for this vaccine, a theoretical risk of incidental exposure exists via pharyngeal or faecal shedding from vaccinated children in the household or close community. METHODS: This was an observational study of pregnant women conducted in Nampula (exposed cohort) and Maputo (non-exposed cohort) in Mozambique from August 2022 to June 2023. Two nOPV2 campaigns were conducted in Nampula and none in Maputo. Women were followed-up during routine prenatal consultation, delivery, and 28-day neonate visits for obstetric anomalies and pregnancy outcomes. Sociodemographic, medical, and obstetric history was captured. RESULTS: Three hundred twenty-six pregnant women were enrolled from Nampula and 940 from Maputo City. Stillbirth prevalence (2·3% vs 1·6%, p = 0·438), low birth weight (8·9% vs 8·2%, p = 0·989), congenital anomalies (1 % vs 0·5%, p = 0·454), neonatal death (2·3% vs 1·6%, p = 0·08), and maternal death (0 % vs 0·2%, p = 0·978) did not differ amongst exposed and non-exposed cohorts. There was an increased rate of pre-term delivery in the exposed cohort (18·4% vs 11·0%, p = 0·011). CONCLUSION: We did not observe an increased frequency of adverse pregnancy outcomes due to passive nOPV2 exposure. A higher frequency of preterm delivery needs to be further investigated. The data reported herein support the continued use of nOPV2 for poliovirus outbreak response and full licensure of the vaccine.

Can earlier BCG-Japan and OPV vaccination reduce early infant mortality? A cluster-randomised trial in Guinea-Bissau.

OBJECTIVE: To assess the effect of providing BCG and oral polio vaccine (OPV) at an early home visit after delivery. DESIGN: Cluster-randomised trial, randomising 92 geographically defined clusters 1:1 to intervention/control arms. SETTING: Bandim Health Project Health and Demographic Surveillance System, Guinea-Bissau. PARTICIPANTS: 2226 newborns enrolled between July 2016 and August 2019. INTERVENTIONS: In both arms, newborns received a home visit within 72 hours after birth. In intervention clusters (n=46), BCG and OPV were provided at the home visit. MAIN OUTCOME MEASURE: Rates of non-accidental mortality were compared in Cox proportional hazards models from (last of) day 1 or enrolment, until (first of) day 60 or registration of non-trial vaccines. RESULTS: A total of 35 deaths (intervention: 7, control: 28) were registered during the trial. Providing BCG and OPV reduced non-accidental early infant mortality by 59% (8-82%). The intervention also reduced non-accidental hospital admissions. The intervention had little impact on growth and BCG scarring and tended to increase the risk of consultations. CONCLUSIONS: The trial was stopped early due to lower-than-expected enrolment and event rates when 33% of the planned number of newborns had been enrolled. Despite the small size of the trial, the results support that early BCG and OPV vaccinations are beneficial and reduce early child mortality and morbidity. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Registry (NCT02504203).

Safety of the novel oral poliovirus vaccine type 2 (nOPV2) in infants and young children aged 1 to <5 years and lot-to-lot consistency of the immune response to nOPV2 in infants in The Gambia: a phase 3, double-blind, randomised controlled trial.

BACKGROUND: Novel oral poliovirus vaccine type 2 (nOPV2) has been engineered to improve the genetic stability of Sabin oral poliovirus vaccine (OPV) and reduce the emergence of circulating vaccine-derived polioviruses. This trial aimed to provide key safety and immunogenicity data required for nOPV2 licensure and WHO prequalification. METHODS: This phase 3 trial recruited infants aged 18 to <52 weeks and young children aged 1 to <5 years in The Gambia. Infants randomly assigned to receive one or two doses of one of three lots of nOPV2 or one lot of bivalent OPV (bOPV). Young children were randomised to receive two doses of nOPV2 lot 1 or bOPV. The primary immunogenicity objective was to assess lot-to-lot equivalence of the three nOPV2 lots based on one-dose type 2 poliovirus neutralising antibody seroconversion rates in infants. Equivalence was declared if the 95% CI for the three pairwise rate differences was within the -10% to 10% equivalence margin. Tolerability and safety were assessed based on the rates of solicited adverse events to 7 days, unsolicited adverse events to 28 days, and serious adverse events to 3 months post-dose. Stool poliovirus excretion was examined. The trial was registered as PACTR202010705577776 and is completed. FINDINGS: Between February and October, 2021, 2345 infants and 600 young children were vaccinated. 2272 (96·9%) were eligible for inclusion in the post-dose one per-protocol population. Seroconversion rates ranged from 48·9% to 49·2% across the three lots. The minimum lower bound of the 95% CIs for the pairwise differences in seroconversion rates between lots was -5·8%. The maximum upper bound was 5·4%. Equivalence was therefore shown. Of those seronegative at baseline, 143 (85·6%) of 167 (95% CI 79·4-90·6) infants and 54 (83·1%) of 65 (71·7-91·2) young children seroconverted over the two-dose nOPV2 schedule. The post-two-dose seroprotection rates, including participants who were both seronegative and seropositive at baseline, were 604 (92·9%) of 650 (95% CI 90·7-94·8) in infants and 276 (95·5%) of 289 (92·4-97·6) in young children. No safety concerns were identified. 7 days post-dose one, 78 (41·7%) of 187 (95% CI 34·6-49·1) infants were excreting the type 2 poliovirus. INTERPRETATION: nOPV2 was immunogenic and safe in infants and young children in The Gambia. The data support the licensure and WHO prequalification of nOPV2. FUNDING: Bill & Melinda Gates Foundation.

Factors associated with full childhood vaccination coverage among young mothers in Northern Nigeria.

Introduction: wide regional variation in immunization coverage still persists in Nigeria. Full Immunization Coverage (FIC) for more than 80% of all states in the northern region is lower than 40% relative to their southern counterpart. Studies focusing on young women in the north remain sparse, despite the high prevalence of early marriage and poor health-seeking behavior. This study examines FIC among young women in northern Nigeria. Methods: we performed a secondary analysis of the 2013 and 2018 Nigeria Demographic and Health Survey on 1,198 women of children aged 12-23 months in 2013 and 405 in the 2018 dataset. Analysis was limited to young women 15-24 years, residing in Northern Nigeria. We used logistics regression to predict factors associated with FIC. Results: the proportion of fully immunized children was low, at 11% in 2013 and 18% in 2018. The coverage for most vaccines was low, except for the oral polio vaccine. The children of mothers who had health card [(aOR=18.1,95% C.I (8.1-40.7)], in 2013 and 2018 [(aOR=12.7, 95% C.I (5.9-27.1)], attended ANC [(aOR=8.6, 95% C.I (2.4-30.9)] in 2013 and had facility delivery [(aOR=2.0, 95% C.I (1.0-4.1)] in 2018 were more likely to be fully immunized. Conclusion: the study found FIC among children of young women in Northern Nigeria was abysmally low. Ownership of health care, antenatal attendance, and facility delivery significantly predicted the odds of FIC. These findings suggest the need for approaches that remove barriers to good health-seeking behavior, especially among young mothers in Northern Nigeria.