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Introduction: The Canadian National Vaccine Safety Network (CANVAS) conducted active participant-based surveillance for adverse events following immunization during the COVID-19 vaccine campaign. This study evaluated the association between COVID-19 vaccination and neurological adverse events., Methods: Participants were invited to complete online surveys to report health events that prevented daily activities and/or required medical attention within 7 days after COVID-19 vaccination or 7 days prior to the survey (unvaccinated controls); follow-up surveys were sent 7 months later. Neurological events were health events where the most severe symptom reported was ≥1 of: numbness/tingling, loss of taste or smell, vision loss, facial weakness/paralysis, seizure, weakness/paralysis of arms or legs, confusion, change in personality or behavior, or difficulty with urination or defecation. Data were extracted from the CANVAS-COVID database for analysis., Results: Completed survey responses were received from 15,273 unvaccinated controls, 758,619 dose 1 recipients, 406,884 dose 2 recipients, and 126,586 dose 3 recipients. Rates of neurological events ranged from 15.9 (95 % CI 13.6-18.4) per 10,000 dose 1 ChAdOx1 recipients to 8.4 (6.5-10.8) and 7.9 (5.7-11.0) per 10,000 dose 3 mRNA-1273 and BNT162b2 recipients, respectively. Multivariable regression adjusted for age, sex, previous SARS-CoV-2 infection, and baseline health status showed an increased risk of neurological event among ChAdOx1 dose 1 recipients versus controls (adjusted OR 2.3, 95 % CI 1.2-4.3), but not among mRNA vaccine recipients after any dose. Risk of anaesthesia/paresthesia were increased following ChAdOx1 dose 1 (aOR 4.7, 1.7-13.1), and consistently but not statistically significantly higher following any dose of either mRNA vaccine. Risk of loss of smell/taste was decreased among recipients of any dose of either mRNA vaccine versus controls., Conclusions: The results support the safety of COVID-19 vaccines while confirming reported associations between ChAdOx1 dose 1 and neurological events. Participant-based AEFI surveillance is a useful component of post-market surveillance programs., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Julie A Bettinger reports financial support was provided by Canadian Institutes of Health Research. Julie A Bettinger reports financial support was provided by Public Health Agency of Canada. Manish Sadarangani reports financial support was provided by BC Children’s Hospital Foundation. Manish Sadarangani reports financial support was provided by Michael Smith Foundation for Health Research. M Sadarangani, OG Vanderkooi, JE Isenor reports a relationship with GlaxoSmithKline Inc that includes: funding grants. M Sadarangani, OG Vanderkooi, JD Kellner reports a relationship with Merck & Co Inc that includes: funding grants. M Sadarangani, JD Kellner reports a relationship with Moderna Inc that includes: funding grants. M Sadarangani, OG Vanderkooi, JD Kellner, L Valiquette reports a relationship with Pfizer Inc that includes: funding grants. M Sadarangani, JE Isenor reports a relationship with Sanofi Pasteur Inc that includes: funding grants. OG Vanderkooi reports a relationship with Seqirus Inc that includes: funding grants. A McGeer reports a relationship with GlaxoSmithKline Inc, Merck & Co Inc, Pfizer Inc, Sanofi Pasteur Inc, Seqirus Inc that includes: consulting or advisory and funding grants. A McGeer reports a relationship with Moderna Inc, AstraZeneca Canada Inc, Medicago Inc that includes: consulting or advisory and speaking and lecture fees. KA Top reports a relationship with Coalition for Epidemic Preparedness Innovations that includes: funding grants. 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.)

MVA-BN is an orthopoxvirus vaccine that provides protection against both smallpox and mpox. In June 2022, Canada launched a publicly-funded vaccination campaign to offer MVA-BN to at-risk populations including men who have sex with men (MSM) and sex workers. The safety of MVA-BN has not been assessed in this context. To address this, the Canadian National Vaccine Safety Network (CANVAS) conducted prospective safety surveillance during public health vaccination campaigns in Toronto, Ontario and in Vancouver, British Columbia. Vaccinated participants received a survey 7 and 30 days after each MVA-BN dose to elicit adverse health events. Unvaccinated individuals from a concurrent vaccine safety project evaluating COVID-19 vaccine safety were used as controls. Vaccinated and unvaccinated participants that reported a medically attended visit on their 7-day survey were interviewed. Vaccinated participants and unvaccinated controls were matched 1:1 based on age group, gender, sex and provincial study site. Overall, 1,173 vaccinated participants completed a 7-day survey, of whom 75 % (n = 878) also completed a 30-day survey. Mild to moderate injection site pain was reported by 60 % of vaccinated participants. Among vaccinated participants 8.4 % were HIV positive and when compared to HIV negative vaccinated individuals, local injection sites were less frequent in those with HIV (48 % vs 61 %, p = 0.021), but health events preventing work/school or requiring medical assessment were more frequent (7.1 % vs 3.1 %, p = 0.040). Health events interfering with work/school, or requiring medical assessment were less common in the vaccinated group than controls (3.3 % vs. 7.1 %, p < 0.010). No participants were hospitalized within 7 or 30 days of vaccination. No cases of severe neurological disease, skin disease, or myocarditis were identified. Our results demonstrate that the MVA-BN vaccine appears safe when used for mpox prevention, with a low frequency of severe adverse events and no hospitalizations observed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. This study was funded by a grant from the Canadian Institutes of Health Research and the Public Health Agency of Canada (FRN#178755)., (Copyright © 2023 Elsevier Ltd. All rights reserved.)