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The following is a summary of “Relative vaccine protection, disease severity, and symptoms associated with the SARS-CoV-2 omicron subvariant BA.2.86 and descendant JN.1 in Denmark: a nationwide observational study,” published in the September 2024 issue of Infectious Disease by Moustsen-Helms et al.
In the 2023 Danish COVID-19 vaccination campaign, an updated monovalent mRNA vaccine targeting the SARS-CoV-2 omicron XBB.1.5 subvariant was administered. However, the emergence and immediate spread of the genetically divergent omicron BA.2.86 subvariant, JN.1, since September 2023 raises concerns about its potential for immune escape and dominance.
Researchers conducted a retrospective study using national electronic health registry data to evaluate whether the SARS-CoV-2 subvariant BA.2.86 and its descendant JN.1 differed from other variants in vaccine escape, risk of severe disease, and self-reported symptoms.
They examined Danish residents aged ≥65 years who tested positive for SARS-CoV-2 by PCR (Oct 1-Dec 31, 2023) with available genomic data. Clinical testing, sentinel, and self-sampling-based surveillance data were related to national electronic civil, vaccination, and hospitalization registers. The relative protection of the XBB.1.5 updated COVID-19 vaccine against BA.2.86 infections vs other variants was analyzed in a case-only study, and the relative risk of hospitalization for BA.2.86 vs other variants was also examined, adjusted for time, comorbidities, and previous vaccination history. Prevalence patterns of self-reported symptoms among infected individuals of all ages were reported separately by subvariant.
The results showed that 3,862 of 7,581 Danish residents aged ≥65 years who tested positive for SARS-CoV-2 (Oct 1-Dec 31, 2023) were examined; of these, 2,184 (57%) were infected with BA.2.86, including 1,615 JN.1 infections. Participants infected with BA.2.86 (1.52) and JN.1 (1.60) had higher odds of receiving the XBB.1.5 vaccine than those infected with non-BA.2.86 variants. However, there was no evidence of an association between the infecting variant and the risk of COVID-19 hospitalization (BA.2.86: 1.04, JN.1: 1.07) or differences in self-reported symptoms.
They concluded in comparison to other SARS-CoV-2 variants, BA.2.86 and JN.1 were less susceptible to vaccine-induced immune protection from the XBB.1.5 updated COVID-19 vaccine; however, there was no evidence of increased disease severity or different symptom profiles associated with these variants. Despite reduced effectiveness against the new variants, XBB.1.5 vaccination remains protective and reduces the risk of infection and COVID-19 disease.
Source: thelancet.com/journals/laninf/article/PIIS1473-3099(24)00220-2/fulltext
