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Background: Interpretations of pediatric COVID-19 severity are complicated by novel lineages and COVID-19 vaccine introduction. We estimated the risk of severe COVID-19 by SARS-CoV-2 lineage and vaccination status among hospitalized Canadian children., Methods: Data were collected through the Canadian Paediatric Surveillance Program (April 2020-May 2021) and Canadian Immunization Monitoring Program, ACTive (June 2021-December 2022). Patients <17 years hospitalized for COVID-19 (excluding incidental SARS-CoV-2) at 13 pediatric hospitals were included. Lineages were defined via genetic sequencing or dominant lineage upon hospitalization. Severe disease included intensive care, ventilatory/hemodynamic requirements, systemic complications, and/or death., Results: We analyzed 3218 COVID-19 hospitalizations, including 81.4% admitted during Omicron predominance. Median age was highest among Delta cases (2.9 years, interquartile range [IQR] 0.2-10.9) and lowest among Omicron BQ.1 cases (0.6 years, IQR 0.2-1.8). Severe COVID-19 remained common in Omicron vs. ancestral cases (27.2% vs. 23.2%). The proportion of hospitalized cases aged 5-16 years declined following the introduction of age-specific COVID-19 vaccines. Vaccination reduced the risk of in-hospital severe disease for ages 12-16 years (two vs. zero doses; adjusted risk ratio 0.49, 95% confidence interval 0.32-0.77)., Conclusion: More children were hospitalized with Omicron lineages than all prior lineages. COVID-19 vaccination was associated with a lower burden of severe disease among ages 5-16 years., Impact Statement: This study estimates the effect of SARS-CoV-2 lineage, Omicron sub-lineage, and vaccination on COVID-19 disease severity, using data from two Canadian national surveillance programs. Few national studies describe the clinical presentation and severity of Omicron sub-lineages among hospitalized children. In Canada, Omicron lineages were associated with substantially more pediatric COVID-19 hospitalizations than all prior lineages combined, though risk of severe COVID-19 was highest during the Delta period. COVID-19 vaccines were associated with reductions in hospitalization (ages 5-16 years) and severe disease (ages 12-16 years) across Omicron sub-lineages., Competing Interests: Competing interests: O.D. and F.K. are supported by a Clinical Research Scholars Award from the Fonds de recherche du Québec—Santé. S.A.H. received funding from multiple vaccine manufacturers to undertake phase 1–3 clinical trials of candidate COVID-19 vaccines. J.P. reported grants from Merck, and personal fees from Enanta, outside the submitted work. M.S. is supported via salary awards from the BC Children’s Hospital Foundation and Michael Smith Health Research BC. M.S. has also been an investigator on projects funded by GlaxoSmithKline, Merck, Moderna, Pfizer, and Sanofi-Pasteur. All funds have been paid to his institute, and he has not received any personal payments. K.A.T. received grants from the Coalition for Epidemic Preparedness Innovations outside the submitted work. S.K.M. has received honoraria for lectures from GlaxoSmithKline and Sanofi Pasteur and has been a member of ad hoc advisory boards for Pfizer, Sanofi Pasteur, and Apotex, all unrelated to this study. All other authors have no conflicts of interest to disclose. Consent statement: The CPSP collects data elements for national child and youth health surveillance purposes on PHAC’s behalf, whose purpose is to support health protection and promotion under the Department of Health Act 4(2)c and the Public Health Agency of Canada Act 3(15). Healthcare providers are authorized under their provincial health privacy legislation (with the exception of Quebec) to disclose protected health information to public health agencies at the local, provincial, and federal levels for surveillance purposes. CPSP does not collect any individual data elements deemed to be unique identifiers. In Quebec, CPSP studies are conducted under center-specific research ethics board approvals and data transfer agreements. This is consistent with the Canadian Medical Association and Tri-Council Policy Statements, which allow for the collection of non-nominal and nonidentifiable information for conditions under surveillance. For the IMPACT COVID-19, investigators at each IMPACT center also obtained Research Ethics Board or hospital approvals from their institution, and received waivers of consent for secondary use of patient-level data., (© 2025. The Author(s), under exclusive licence to the International Pediatric Research Foundation, Inc.)

Purpose: Many individuals with inborn errors of immunity (IEIs) have poor humoral immune (HI) vaccine responses. Only a few studies have examined specific cell-mediated immune (CMI) responses to coronavirus disease 2019 (COVID-19) vaccines in this population. Therefore, the purpose of this study was to examine HI and CMI responses up to 6 months post-COVID-19 vaccine dose 3 in adults with IEIs., Methods: A multi-center prospective observational study was conducted across Canada to collect severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-specific HI and CMI data at 4- and 24-week intervals after vaccine doses 2 and 3 (D2 + 4wk/D2 + 24wk/D3 + 4wk/D3 + 24wk)., Results: A total of 149 adults with IEIs and 423 healthy controls were recruited from July 2021 to October 2023. Geometric mean anti-spike IgG (binding antibody units/mL) and spike-specific T-cell responses [IFN-γ + T cells/10 6 peripheral blood mononuclear cells (PBMCs)] were significantly lower in IEIs compared to controls at D2 + 4wk, D3 + 4wk, and D3 + 24wk. However, at 6 months after completing the primary series (three doses for IEIs and two doses for healthy), both HI and CMI responses of both IEI participants and healthy controls persisted and were comparable. There was a strong correlation between neutralizing antibody titer (ID50) and anti-spike IgG but not between ID50 and CMI. There was only one reported case of hospitalized COVID-19 disease before and none after completing the primary series among IEI participants., Conclusion: Adults with IEIs mounted both HI and CMI responses following COVID-19 vaccines, which were lower than those of healthy individuals but were present at least up to 6 months after dose 3. These data support the initial recommendation for a three-dose primary series among IEIs., Competing Interests: HC has received consultation, speaker fees, and educational funding not related to this study from Takeda, CSL Behring, Pharming, Sanofi, Novartis, Sobi, Pharvaris, and KalVista. KT receives grants from the Coalition for Epidemic Preparedness Innovations outside the submitted work. BD received consultation and speaker fees from Takeda and Pharming, not related to this study. MS has been an investigator on projects funded by GlaxoSmithKline, Merck, Moderna, Pfizer, and Sanofi-Pasteur. All funds have been paid to his institute, and he has not received any personal payments. JC has received consultation, speaker fees, and educational funding not related to this study from Takeda, CSL Behring, Grifols, Octapharma, GSK, Pfizer, AstraZeneca, EMD Serono, and Avir Pharma. LM-F is a member of the Data Safety Monitoring Committee for Encoded Therapeutics and has participated as an Advisory Board Member for Takeda, both unrelated to the submitted work. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2025 Unninayar, Falcone, Chapdelaine, Vinh, Top, Derfalvi, Issekutz, Decaluwe, Pham-Huy, Upton, Betschel, Rubin, Suresh, Wright, Murguía-Favela, Kalashnikova, Barrett, Oldford, Langlois, Arnold, Sadarangani, Zhang, Ramsay, Yazji and Cowan.)

Lassa virus (LASV) belongs to the Arenavirus family. LASV is endemic in several West Africa countries and causes viral hemorrhagic fevers. The Nigeria CDC has reported that an outbreak in 2024 in 28 states has resulted in 7767 suspected cases of Lassa fever, 971 confirmed cases and 166 confirmed deaths up to 11 August. Since infection with LASV can result in sensorineural hearing loss (SNHL) in up to 30% of patients, there are questions about whether triggering the immune response by immunization with LASV vaccines could potentially cause SNHL, although this has not been shown in clinical trials to date. To address this issue, the Coalition for Epidemic Preparedness Innovations (CEPI) and the Brighton Collaboration (BC) Safety Platform for Emergency vACcines (SPEAC) convened a three-hour webinar on 22 September 2023 to review what is known from both animal studies and human clinical trials and how hearing assessments in future clinical trials can help to assess the risk. This report summarizes the evidence presented and provides considerations for hearing assessment in expanded human trials of LASV vaccine candidates in children and adults., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Cornelia L. Dekker reports a relationship with The Task Force for Global Health that includes: consulting or advisory. Cornelia L. Dekker reports a relationship with Dynavax Technologies, Inc. that includes: equity or stocks. Nicholas S. Reed reports a relationship with Neosensory Inc. that includes: consulting or advisory. Carmen C. Brewer reports a relationship with Emergent Product Development that includes: consulting or advisory. Carmen C. Brewer reports a relationship with International Aids Vaccine Initiative that includes: consulting or advisory. Gideon Akintunde reports a relationship with Emergent BioSolutions Inc. that includes: equity or stocks. Lovelyn Charles reports a relationship with Emergent BioSolutions Inc. that includes: employment. Patricia Fast reports a relationship with International Aids Vaccine Initiative that includes: employment. Daniel D. Pinschewer reports a relationship with HOOKIPA Pharma Inc. that includes: consulting or advisory, equity or stocks, funding grants, and travel reimbursement. Daniel D. Pinschewer reports a relationship with Dodet Bioscience that includes: speaking and lecture fees. Karina A. Top reports a relationship with Coalition for Epidemic Preparedness Innovations that includes: funding grants. Steven B. Black reports a relationship with Coalition for Epidemic Preparedness Innovations that includes: funding grants. Daniel D. Pinschewer has patent with royalties paid to Licensee. Co-author editorial board for Ear and Hearing - CCB If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)