Oral Poliovirus Vaccine Research Articles

Increasing Population Immunity Prior to Globally-Coordinated Cessation of Bivalent Oral Poliovirus Vaccine (bOPV).

In 2022, global poliovirus modeling suggested that coordinated cessation of bivalent oral poliovirus vaccine (bOPV, containing Sabin-strain types 1 and 3) in 2027 would likely increase the risks of outbreaks and expected paralytic cases caused by circulating vaccine-derived polioviruses (cVDPVs), particularly type 1. The analysis did not include the implementation of planned, preventive supplemental immunization activities (pSIAs) with bOPV to achieve and maintain higher population immunity for types 1 and 3 prior to bOPV cessation. We reviewed prior published OPV cessation modeling studies to support bOPV cessation planning. We applied an integrated global poliovirus transmission and OPV evolution model after updating assumptions to reflect the epidemiology, immunization, and polio eradication plans through the end of 2023. We explored the effects of bOPV cessation in 2027 with and without additional bOPV pSIAs prior to 2027. Increasing population immunity for types 1 and 3 with bOPV pSIAs (i.e., intensification) could substantially reduce the expected global risks of experiencing cVDPV outbreaks and the number of expected polio cases both before and after bOPV cessation. We identified the need for substantial increases in overall bOPV coverage prior to bOPV cessation to achieve a high probability of successful bOPV cessation.

Monitoring the VDPV2 outbreak in Egypt during 2020–2021 highlights the crucial role of environmental surveillance and boosting immunization in combating Poliovirus

BackgroundPoliovirus is a highly infectious enterovirus (EV) that primarily affects children and can lead to lifelong paralysis or even death. Vaccine-derived polioviruses (VDPVs) are a great threat since they are derived from the attenuated virus in the Oral Poliovirus Vaccine (OPV) and can mutate to a more virulent form. The purpose of this study was to identify VDPV serotype 2 through the year 2020–2021 via surveillance of sewage samples collected from different localities and governorates in Egypt and stool specimens from Acute Flaccid Paralysis (AFP) cases. Both were collected through the national poliovirus surveillance system and according to the guidelines recommended by the WHO.MethodsA total of 1266 sewage samples and 3241 stool samples from January 2020 to December 2021 were investigated in the lab according to World Health Organization (WHO) protocol for the presence of Polioviruses by cell culture, molecular identification of positive isolates on L20B cell line was carried out using real-time polymerase chain reactions (RT-PCR). Any positive isolates for Poliovirus type 2 and isolates suspected of Vaccine Derived Poliovirus Type 1 and type 3 screened by (VDPV1) or Vaccine Poliovirus Type 3 (VDPV3) assay in RT-PCR were referred for VP1 genetic sequencing.ResultsThe outbreak was caused by circulating VDPV2 (cVDPV2) strains started in January 2021. By the end of February 2021, a total of 11 cVDPV2s were detected in sewage samples from six governorates confirming the outbreak situation. One additional cVDPV2 was detected later in the sewage sample from Qena (June 2021). The first and only re-emergence of VDPV2 in stool samples during the outbreak was in contact with Luxor in June 2021. By November 2021, a total of 80 VDPVs were detected. The Egyptian Ministry of Health and Population (MOHP), in collaboration with the WHO, responded quickly by launching two massive vaccination campaigns targeting children under the age of five. Additionally, surveillance systems were strengthened to detect new cases and prevent further spread of the virus.ConclusionThe continued threat of poliovirus and VDPVs requires ongoing efforts to prevent their emergence and spread. Strategies such as improving immunization coverage, using genetically stable vaccines, and establishing surveillance systems are critical to achieving global eradication of poliovirus and efficient monitoring of VDPVs outbreaks.

Safety and Immunogenicity of Trivalent Oral Polio Vaccine in Vaccinated Children and Vaccine-Naïve Infants: A Phase 4 Study.

In the context of polio eradication, novel oral polio vaccines for type 2 (nOPV2) were developed, and types 1 and 3 polioviruses are being developed. We aimed to generate trivalent oral poliovirus vaccine (tOPV) safety and immunogenicity data as a reference for comparing with novel OPV formulations. This was a single-center, open-label, phase 4 study in March 2016 in the Dominican Republic with healthy children previously vaccinated with ≥3 doses of tOPV receiving one dose of tOPV and vaccine-naïve infants receiving 3 doses of tOPV. Safety and immunogenicity were assessed. No serious adverse reactions or important medical reactions were reported. Seroconversion (SC) rates at Day 28 in children were 32.7%, 36.7%, and 46.9% for types 1, 2, and 3, respectively, and seroprotection (SP) rates 28 days after one dose increased from 89.8% at baseline to 93.9%, 98.0% to 100%, and 83.7% to 98.0% for types 1, 2, and 3, respectively. In infants, SC rates were 88.5%, 98.1%, and 96.2% for types 1, 2, and 3, respectively. SP rates at Day 84 were 93.3%, 100%, and 96.2% for types 1, 2, and 3, respectively. This information can be used as a reference to compare with novel monovalent or trivalent OPVs under development.

Assessing the mucosal intestinal and systemic humoral immunity of sequential schedules of inactivated poliovirus vaccine and bivalent oral poliovirus vaccine for essential immunization in Bangladesh: An open-label, randomized controlled trial

In 2012, the Strategic Advisory Group of Experts on Immunization (SAGE) recommended introduction of at least one inactivated poliovirus vaccine (IPV) dose in essential immunization programs. We evaluated systemic humoral and intestinal mucosal immunity of a sequential IPV-bivalent oral poliovirus vaccine (bOPV) schedule compared with a co-administration IPV + bOPV schedule in an open-label, randomized, controlled, non-inferiority, inequality trial in Dhaka, Bangladesh. Healthy infants aged 6 weeks were randomized to either: (A) IPV and bOPV at 6 and bOPV at 10 and 14 weeks (IPV + bOPV-bOPV-bOPV); or (B) IPV at 6 and bOPV at 10 and 14 weeks (IPV-bOPV-bOPV). Of 456 participants enrolled and randomly assigned during May–August 2015, 428 (94%) were included in the modified intention-to-treat analysis (arm A: 211, arm B: 217). Humoral immune responses did not differ at 18 weeks between study arms: type 1 (98% versus 96%; p = 0.42), type 2 (37% versus 39%; p = 0.77), and type 3 (97% versus 93%; p = 0.07). Virus shedding one week after the bOPV challenge dose in arm B was non-inferior to arm A (type 1 difference = −3% [90% confidence interval: −6 − 0.4%]; type 3 difference: −3% [−6 to −0.2%]). Twenty-six adverse events including seven serious adverse events were reported among 25 participants including one death; none were attributed to study vaccines.An IPV-bOPV-bOPV sequential schedule induced comparable systemic humoral immunity to all poliovirus types and types 1 and 3 intestinal mucosal immunity as an IPV + bOPV-bOPV-bOPV co-administration schedule.

Health and Economic Benefits of Routine Childhood Immunizations in the Era of the Vaccines for Children Program - United States, 1994-2023.

Since 1994, the U.S. Vaccines for Children (VFC) program has covered the cost of vaccines for children whose families might not otherwise be able to afford vaccines. This report assessed and quantified the health benefits and economic impact of routine U.S. childhood immunizations among both VFC-eligible and non-VFC-eligible children born during 1994-2023. Diphtheria and tetanus toxoids and acellular pertussis vaccine; Haemophilus influenzae type b conjugate vaccine; oral and inactivated poliovirus vaccines; measles, mumps, and rubella vaccine; hepatitis B vaccine; varicella vaccine; pneumococcal conjugate vaccine; hepatitis A vaccine; and rotavirus vaccine were included. Averted illnesses and deaths and associated costs over the lifetimes of 30 annual cohorts of children born during 1994-2023 were estimated using established economic models. Net savings were calculated from the payer and societal perspectives. Among approximately 117 million children born during 1994-2023, routine childhood vaccinations will have prevented approximately 508 million lifetime cases of illness, 32 million hospitalizations, and 1,129,000 deaths, at a net savings of $540 billion in direct costs and $2.7 trillion in societal costs. From both payer and societal perspectives, routine childhood vaccinations among children born during 1994-2023 resulted in substantial cost savings. Childhood immunizations continue to provide substantial health and economic benefits, while promoting health equity.

Persistent Transmission of Circulating Vaccine-Derived Poliovirus - Somalia, January 2017-March 2024.

Since the launch of the Global Polio Eradication Initiative in 1988, substantial progress has been made in the interruption of wild poliovirus (WPV) transmission worldwide: global eradication of WPV types 2 and 3 were certified in 2015 and 2019, respectively, and endemic transmission of WPV type 1 continues only in Afghanistan and Pakistan. After the synchronized global withdrawal of all serotype 2 oral poliovirus vaccines (OPVs) in 2016, widespread outbreaks of circulating vaccine-derived poliovirus type 2 (cVDPV2) have occurred, which are linked to areas with low population immunity to poliovirus. Officials in Somalia have detected ongoing cVDPV2 transmission since 2017. Polio vaccination coverage and surveillance data for Somalia were reviewed to assess this persistent transmission. During January 2017-March 2024, officials in Somalia detected 39 cVDPV2 cases in 14 of 20 regions, and transmission has spread to neighboring Ethiopia and Kenya. Since January 2021, 28 supplementary immunization activities (SIAs) targeting cVDPV2 were conducted in Somalia. Some parts of the country are security-compromised and inaccessible for vaccination campaigns. Among 1,921 children with nonpolio acute flaccid paralysis, 231 (12%) had not received OPV doses through routine immunization or SIAs, 95% of whom were from the South-Central region, and 60% of whom lived in inaccessible districts. Enhancing humanitarian negotiation measures in Somalia to enable vaccination of children in security-compromised areas and strengthening campaign quality in accessible areas will help interrupt cVDPV2 transmission.

Application of MPBT Assay for Multiplex Determination of Infectious Titers and for Selection of the Optimal Formulation for the Trivalent Novel Oral Poliovirus Vaccine.

Recently, a multiplex PCR-based titration (MPBT) assay was developed for simultaneous determination of infectious titers of all three Sabin strains of the oral poliovirus vaccine (OPV) to replace the conventional CCID50 assay, which is both time-consuming and laborious. The MPBT assay was shown to be reproducible, robust and sensitive. The conventional and MPBT assays showed similar results and sensitivity. The MPBT assay can be completed in two to three days, instead of ten days for the conventional assay. To prevent attenuated vaccine strains of poliovirus from reversion to virulence, a novel, genetically stable OPV (nOPV) was developed by modifying the genomes of conventional Sabin strains used in OPV. In this work, we evaluated the MPBT assay as a rapid screening tool to support trivalent nOPV (tnOPV) formulation development by simultaneous titration of the three nOPV strains to confirm stability as needed, for the selection of the lead tnOPV formulation candidate. We first assessed the ability of the MPBT assay to discriminate a 0.5 log10 titer difference by titrating the two tnOPV samples (undiluted and threefold-diluted) on the same plate. Once the assay was shown to be discriminating, we then tested different formulations of tnOPV drug products (DPs) that were subjected to different exposure times at 37 °C (untreated group and treated groups: 2 and 7 days at 37 °C), and to three freeze and thaw (FT) cycles. Final confirmation of the down selected formulation candidates was achieved by performing the conventional CCID50 assay, comparing the stability of untreated and treated groups and FT stability testing on the top three candidates. The results showed that the MPBT assay generates similar titers as the conventional assay. By testing two trivalent samples in the same plate, the assay can differentiate a 0.5 log10 difference between the titers of the tested nOPV samples. Also, the assay was able to detect the gradual degradation of nOPV viruses with different formulation compositions and under different time/temperature conditions and freeze/thaw cycles. We found that there were three tnOPV formulations which met the stability criteria of less than 0.5 log10 loss after 2 days' exposure to 37 ℃ and after three FT cycles, maintaining the potency of all three serotypes in these formulations. The ability of the MPBT assay to titrate two tnOPV lots (six viruses) in the same plate makes it cheaper and gives it a higher throughput for rapid screening. The assay detected the gradual degradation of the tnOPV and was successful in the selection of optimal formulations for the tnOPV. The results demonstrated that the MPBT method can be used as a stability indicating assay to assess the thermal stability of the nOPV. It can be used for rapid virus titer determination during the vaccine manufacturing process, and in clinical trials. The MPBT assay can be automated and applied for other viruses, including those with no cytopathic effect.

Vaccine-associated paralytic poliomyelitis in oral polio vaccine recipients: disproportionality analysis using VAERS and systematic review

ABSTRACT Background Vaccine-associated paralytic poliomyelitis (VAPP) is a rare adverse event of oral poliovirus vaccines (OPV), particularly affecting immunodeficient individuals. Research design and methods This study aimed to (1) Assess the association between OPV and VAPP using Vaccine Adverse Event Reporting System (VAERS) database (2) Outline patient characteristics and risk factors associated with the occurrence of VAPP in OPV recipients through a systematic review of case reports and case series. A disproportionality analysis was conducted using the data from VAERS, encompassing adverse events reported from 1990 till February 2023. Additionally, we conducted a systematic review of case reports and case series using PubMed, Scopus, and Embase databases. Results The VAERS data revealed 130 VAPP reports among 1,739,903 OPV linked adverse events, with year 2010 reporting the strongest association. The systematic review of 37 studies highlighted VAPP occurrence within 2 months to 4 years post-vaccination, typically with acute flaccid paralysis. Immunodeficiency and perianal abscess emerged as major risk factors. Out of the 37 included studies, 27 showed consistent causal association of VAPP with OPV using WHO-AEFI causality assessment tool. Conclusion The study emphasized the seriousness of VAPP and highlights its association with OPV, identifying immunodeficiency as a prominent contributor to VAPP manifestation.

Immunogenicity evaluation of primary polio vaccination schedule with inactivated poliovirus vaccines and bivalent oral poliovirus vaccine

BackgroundTo assess the immunogenicity of the current primary polio vaccination schedule in China and compare it with alternative schedules using Sabin or Salk-strain IPV (sIPV, wIPV).MethodsA cross-sectional investigation was conducted at four sites in Chongqing, China, healthy infants aged 60–89 days were conveniently recruited and divided into four groups according to their received primary polio vaccination schedules (2sIPV + bOPV, 2wIPV + bOPV, 3sIPV, and 3wIPV). The sero-protection and neutralizing antibody titers against poliovirus serotypes (type 1, 2, and 3) were compared after the last dose.ResultsThere were 408 infants completed the protocol. The observed seropositivity was more than 96% against poliovirus types 1, 2, and 3 in all groups. IPV-only groups induced higher antibody titers(GMT) against poliovirus type 2 (Median:192, QR: 96–384, P<0.05) than the “2IPV + bOPV” group. While the “2IPV + bOPV” group induced significantly higher antibody titers against poliovirus type 1 (Median:2048, QR: 768–2048, P<0.05)and type 3 (Median:2048, QR: 512–2048, P<0.05) than the IPV-only group.ConclusionsOur findings have proved that the two doses of IPV with one dose of bOPV is currently the best polio routine immunization schedule in China.

Review of Poliovirus Transmission and Economic Modeling to Support Global Polio Eradication: 2020-2024.

Continued investment in the development and application of mathematical models of poliovirus transmission, economics, and risks leads to their use in support of polio endgame strategy development and risk management policies. This study complements an earlier review covering the period 2000-2019 and discusses the evolution of studies published since 2020 by modeling groups supported by the Global Polio Eradication Initiative (GPEI) partners and others. We systematically review modeling papers published in English in peer-reviewed journals from 2020-2024.25 that focus on poliovirus transmission and health economic analyses. In spite of the long-anticipated end of poliovirus transmission and the GPEI sunset, which would lead to the end of its support for modeling, we find that the number of modeling groups supported by GPEI partners doubled and the rate of their publications increased. Modeling continued to play a role in supporting GPEI and national/regional policies, but changes in polio eradication governance, decentralized management and decision-making, and increased heterogeneity in modeling approaches and findings decreased the overall impact of modeling results. Meanwhile, the failure of the 2016 globally coordinated cessation of type 2 oral poliovirus vaccine use for preventive immunization and the introduction of new poliovirus vaccines and formulation, increased the complexity and uncertainty of poliovirus transmission and economic models and policy recommendations during this time.

The Immunogenicity of Monovalent Oral Poliovirus Vaccine Type 1 (mOPV1) and Inactivated Poliovirus Vaccine (IPV) in the EPI Schedule of India.

In 2016, the Global Polio Eradication Initiative (GPEI) recommended the cessation of using type 2 oral poliovirus vaccine (OPV) and OPV, with countries having to switch from the trivalent to bivalent OPV (bOPV) with the addition of inactivated poliovirus vaccine (IPV) in their routine immunization schedule. The current GPEI strategy 2022-2026 includes a bOPV cessation plan and a switch to IPV alone or a combination of vaccine schedules in the future. The focus of our study was to evaluate the immunogenicity of monovalent OPV type 1 (mOPV1) with IPV and IPV-only schedules. This was a three-arm, multi-center randomized-controlled trial conducted in 2016-2017 in India. Participants, at birth, were randomly assigned to the bOPV-IPV (Arm A) or mOPV1-IPV (Arm B) or IPV (Arm C) schedules. Serum specimens collected at birth and at 14, 18, and 22 weeks old were analyzed with a standard microneutralization assay for all the three poliovirus serotypes. The results of 598 participants were analyzed. The type 1 cumulative seroconversion rates four weeks after the completion of the schedule at 18 weeks were 99.5% (97.0-99.9), 100.0% (97.9-100.0), and 96.0% (92.0-98.1) in Arms A (4bOPV + IPV), B (4mOPV1 + IPV), and C (3IPV), respectively. Type 2 and type 3 seroconversions at 18 weeks were 80.0% (73.7-85.1), 76.9% (70.3-82.4); 93.2% (88.5-96.1), 100.0% (98.0-100.0); and 81.9% (75.6-86.8), 99.4% (96.9-99.9), respectively, in the three arms. This study shows the high efficacy of different polio vaccines for serotype 1 in all three schedules. The type 1 seroconversion rate of mOPV1 is non-inferior to bOPV. All the vaccines provide high type-specific immunogenicity. The program can adopt the use of different vaccines or schedules depending on the epidemiology from time to time.

The Last Mile in Polio Eradication: Program Challenges and Perseverance.

As the Global Polio Eradication Initiative (GPEI) strategizes towards the final steps of eradication, routine immunization schedules evolve, and high-quality vaccination campaigns and surveillance systems remain essential. New tools are consistently being developed, such as the novel oral poliovirus vaccine to combat outbreaks more sustainably, as well as non-infectiously manufactured vaccines such as virus-like particle vaccines to eliminate the risk of resurgence of polio on the eve of a polio-free world. As the GPEI inches towards eradication, re-strategizing in the face of evolving challenges and preparing for unknown risks in the post-certification era are critical.

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.

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

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. 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. 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. 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.

Immune persistence after different polio sequential immunization schedules in Chinese infants

Trivalent oral poliovirus vaccine (tOPV) has been withdrawn and instead an inactivated poliovirus vaccine (IPV) and bivalent type 1 and type 3 OPV (bOPV) sequential immunization schedule has been implemented since 2016, but no immune persistence data are available for this polio vaccination strategy. This study aimed to assess immune persistence following different polio sequential immunization schedules. Venous blood was collected at 24, 36, and 48 months of age from participants who had completed sequential schedules of combined IPV and OPV in phase III clinical trials. The serum neutralizing antibody titers against poliovirus were determined, and the poliovirus-specific antibody-positive rates were evaluated. A total of 1104 participants were enrolled in this study. The positive rates of poliovirus type 1- and type 3-specific antibodies among the sequential immunization groups showed no significant difference at 24, 36, or 48 months of age. The positive rates of poliovirus type 2-specific antibody in the IPV-IPV-tOPV group at all time points were nearly 100%, which was significantly higher than the corresponding rates in other immunization groups (IPV-bOPV-bOPV and IPV-IPV-bOPV). Immunization schedules involving one or two doses of IPV followed by bOPV failed to maintain a high positive rate for poliovirus type 2-specific antibody.

Safety of the novel oral poliovirus vaccine type 2 (nOPV2) in infants and young children aged 1 to

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. 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. 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. nOPV2 was immunogenic and safe in infants and young children in The Gambia. The data support the licensure and WHO prequalification of nOPV2. Bill & Melinda Gates Foundation.

Inactivated Poliovirus Vaccine Booster Reduces the Likelihood of COVID-19 Outcomes in Individuals Primed with Oral Poliovirus Vaccination.

Introduction: Prior research explores whether seasonal and childhood vaccines mitigate the risk of SARS-CoV-2 infection. Although there are trials investigating COVID-19 infection in response to the effects of the oral poliovirus vaccine (OPV), there has been no prior research assessing COVID-19 outcomes in recently immunized adults with the inactivated poliovirus vaccine (IPV). Methods: SARS-CoV-2 infection and COVID-19 symptoms were analyzed across a cohort of 282 adults who received an IPV booster. Bivariate and multivariate regression models explored associations among variables related to vaccination histories and COVID-19 outcomes. Results: One year post-IPV inoculation, participants who had never received OPV were more likely to test positive for SARS-CoV-2 and experience COVID-19 symptoms, compared to those who had previously received OPV (OR = 3.92, 95%CI 2.22-7.03, p < 0.001; OR = 4.45, 95%CI 2.48-8.17, p < 0.001, respectively). Those who had never received OPV experienced COVID-19 symptoms for 6.17 days longer than participants who had previously received OPV (95%CI 3.68-8.67, p < 0.001). Multivariate regression modeling indicated COVID-19 vaccination did not impact SARS-CoV-2 infection or COVID-19 symptoms in this sample of adults who had recently received IPV. Discussion: Findings suggest IPV may boost mucosal immunity among OPV-primed individuals, and COVID-19 vaccination may not provide additional protection among those who had received IPV. Future, larger-scale studies should measure the extent of protective effects against COVID-19 to inform public health policies in resource-deficient settings.

Vitamin D Supplementation and Prior Oral Poliovirus Vaccination Decrease Odds of COVID-19 Outcomes among Adults Recently Inoculated with Inactivated Poliovirus Vaccine.

Structural and functional commonalities between poliovirus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) suggest that poliovirus inoculation may induce antibodies that mitigate the coronavirus disease (COVID-19). No known studies have evaluated COVID-19 risk factors in adults recently vaccinated against poliovirus. Among adults with no history of COVID-19 infection or vaccination, who recently received an inactivated poliovirus vaccine (IPV), we sought to determine which biological factors and social determinants of health (SDOH) may be associated with (1) testing positive for SARS-CoV-2, (2) experiencing COVID-19 symptoms, and (3) a longer duration of COVID-19 symptoms. The influence of biological factors and SDOH on SARS-CoV-2 infection and COVID-19 symptoms were evaluated among 282 adults recently inoculated with IPV. Participant-reported surveys were analyzed over 12 months post-enrollment. Bivariate and multivariate linear and logistic regression models identified associations between variables and COVID-19 outcomes. Adjusting for COVID-19 vaccinations, variants, and other SDOH, secondary analyses revealed that underlying conditions, employment, vitamin D, education, and the oral poliovirus vaccination (OPV) were associated with COVID-19 outcomes. The odds of testing positive for SARS-CoV-2 and experiencing symptoms were significantly reduced among participants who took vitamin D (OR 0.12 and OR 0.09, respectively). Unemployed or part-time working participants were 72% less likely to test positive compared with full-time workers. No prior dose of OPV was one of the strongest predictors of SARS-CoV-2 infection (OR 4.36) and COVID-19 symptoms (OR 6.95). Findings suggest that prophylactic measures and mucosal immunity may mitigate the risk and severity of COVID-19 outcomes. Larger-scale studies may inform future policies.

Effectiveness of poliovirus vaccines against circulating vaccine-derived type 2 poliomyelitis in Nigeria between 2017 and 2022: a case-control study

Between 2018 and 2022, Nigeria experienced continuous transmission of circulating vaccine-derived type 2 poliovirus (cVDPV2), with 526 cases of cVDPV2 poliomyelitis detected in total and approximately 180 million doses of monovalent type 2 oral poliovirus vaccine (mOPV2) and 450 million doses of novel type 2 oral poliovirus vaccine (nOPV2) delivered in outbreak response campaigns. Inactivated poliovirus vaccine (IPV) was introduced into routine immunisation in 2015, with a second dose added in 2021. We aimed to estimate the effectiveness of nOPV2 against cVDPV2 paralysis and compare nOPV2 effectiveness with that of mOPV2 and IPV. In this retrospective case-control study, we used acute flaccid paralysis (AFP) surveillance data in Nigeria from Jan 1, 2017, to Dec 31, 2022, using age-matched, onset-matched, and location-matched cVDPV2-negative AFP cases as test-negative controls. We also did a parallel prospective study from March, 2021, using age-matched community controls from the same settlement as the cases. We included children born after May, 2016, younger than 60 months, for whom polio immunisation history (doses of OPV from campaigns and IPV) was reported. We estimated the per-dose effectiveness of nOPV2 against cVDPV2 paralysis using conditional logistic regression and compared nOPV2 effectiveness with that of mOPV2 and IPV. In the retrospective case-control study, we identified 509 cVDPV2 poliomyelitis cases in Nigeria with case verification and paralysis onset between Jan 1, 2017, and Dec 31, 2022. Of these, 82 children were excluded for not meeting inclusion criteria, and 363 (85%) of 427 eligible cases were matched to 1303 test-negative controls. Cases reported fewer OPV and IPV doses than test-negative controls (mean number of OPV doses 5·9 [SD 4·2] in cases vs 6·7 [4·3] in controls; one or more IPV doses reported in 95 [26%] of 363 cases vs 513 [39%] of 1303 controls). We found low per-dose effectiveness of nOPV2 (12%, 95% CI -2 to 25) and mOPV2 (17%, 3 to 29), but no significant difference between the two vaccines (p=0·67). The estimated effectiveness of one IPV dose was 43% (23 to 58). In the prospective study, 181 (46%) of 392 eligible cases were matched to 1557 community controls. Using community controls, we found a high effectiveness of IPV (89%, 95% CI 83 to 93, for one dose), a low per-dose effectiveness of nOPV2 (-23%, -45 to -5) and mOPV2 (1%, -23 to 20), and no significant difference between the per-dose effectiveness of nOPV2 and mOPV2 (p=0·12). We found no significant difference in estimated effectiveness of the two oral vaccines, supporting the recommendation that the more genetically stable nOPV2 should be preferred in cVDPV2 outbreak response. Our findings highlight the role of IPV and the necessity of strengthening routine immunisation, the primary route through which IPV is delivered. Bill & Melinda Gates Foundation and UK Medical Research Council.

Novel oral poliovirus vaccine type 2 is an important eradication tool, but reaching every last child remains vital

Novel oral poliovirus vaccine type 2 is an important eradication tool, but reaching every last child remains vital