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Relative Vaccine Protection, Disease Severity and Symptoms Associated with Infection with SARS-CoV-2 Omicron Subvariant Ba.2.86 and Descendent Jn.1: A Danish Nationwide Register-Based Study
30 Pages Posted: 8 Feb 2024
More...Abstract
Background: Using nation-wide Danish register data, we investigated whether BA.2.86, including JN.1, differed from other circulating variants in terms of ability to escape vaccine protection, risk of severe disease, and self-reported symptoms.
Methods: We included all Danish residents over 65 years of age with a positive SARS-CoV-2 PCR test and available genomic variant data between October 1, 2023 and December 10, 2023. Data from clinical testing, sentinel and self-sampling-based surveillance were linked with national electronic civil, vaccination and hospitalisation registers. Relative vaccine protection and risk of hospitalisation were analysed in case-control studies adjusted for time, comorbidities, and prior vaccination history among other potential confounders.
Findings: Of the 2,540 COVID-19 cases included in the study, 989 (39%) were infected with the BA.2.86 variant, including 592 JN.1 infections. The adjusted odds of infection with BA.2.86 versus a non-BA.2.86-related variant, were 1.56 (95% CI 1.24–1.96) times higher, and the odds of infection due to JN.1 as opposed to a non-BA.2.86-related variant, were 1.64 (1.24–2.17) times higher for XBB.1.5 vaccinated cases compared to unvaccinated cases. The severity analysis showed no evidence of association between variant and risk of COVID-19 hospitalisation (OR 1.03, 95% CI 0.83–1.28 for BA.2.86 and OR 1.08, 95% CI 0.81–1.43 for JN.1*). Similarly, we found no evidence of differences by variant across self-reported symptoms.
Interpretation:BA.2.86, and in particular the JN.1 sublineage, were less sensitive to vaccine-induced immune protection from the XBB.1.5 updated vaccine, but with no evidence of increased disease severity or different symptom profiles.
Funding: This study was conducted as part of the Danish COVID-19 surveillance. Additional characterisation was supported by co-funding from the European Union’s EU4Health programme under Grant Agreement Nr 101102733 DURABLE. TGL is a fellow of the ECDC Fellowship Programme, supported financially by the European Centre for Disease Prevention and Control.
Declaration of Interest: We have no competing interests to declare.
Ethical Approval: This study was performed under the authority task of the Danish National Infectious Disease Control Institute, which allows Statens Serum Institut to perform analyses on data from existing national COVID-19 surveillance systems. According to Danish law, ethical approval or individual consent is not required for anonymized aggregated register-based studies.
Keywords: COVID-19, variant, severity, vaccine effectiveness
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