WHO: BA.2.86 variantin piirteitä. BA.2.86 ja sen alalinja JN.1 siirretty VOI-varianteiksi 9.2. 2024.

 https://www.who.int/docs/default-source/coronaviruse/21112023_ba.2.86_ire.pdf?sfvrsn=8876def1_3

1
Executive Summary
BA.2.86 has been reported in multiple countries, and the prevalence has been slowly increasing globally.
However, based on the available limited evidence, the public health risk posed by BA.2.86 is currently
evaluated as low at the global level. Current population immunity globally remains highly cross-reactive tothis variant, especially against severe disease but also against symptomatic disease, and therefore the
emergence of this variant will unlikely add increased burden to national public health systems. BA.2.86  classified as variant under monitoring (VUM) on 17 August 2023 and based on updated information, BA.2.86 and its sublineages (including JN.1) are now being classified as a variant of interest (VOI) (9.2. 2024).

Initial Risk Evaluation of BA.2.86 and its sublineages, 

21 November 2023 BA.2.86 is a descendent lineage of BA.2, with the earliest sample collected on 24 July 2023 (1). This variant and its descendent lineages have a large number of mutations in the spike protein; the initially reported BA.2.86 sequences from Israel and Denmark had 34 amino acid substitutions relative to BA.2 and 36  substitutions relative to XBB.1.5 (the strain recommended for the updated COVID-19 vaccine [2]).

 The number of spike amino acid mutations in the BA.2.86 variant relative to BA.2 and XBB.1.5 is comparable to the number of mutations in the first Omicron strains relative to the SARS-CoV-2 index strain. 

 

BA.2.86 was designated as a VUM on 17 August 2023 (3).

As of 20 November 2023, there were 3 267 BA.2.86 sequences submitted to GISAID (1) from 46 countries, representing 8.9% of the globally available sequences in epidemiological week 44 (30 October to 5 November 2023). The largest proportion of BA.2.86 sequences are from the United Kingdom (19.7%, 643 sequences), France (11.9%, 389 sequences), Sweden (10.7%, 351 sequences), Spain (7.8% 254 sequences), Canada (6.8%, 223 sequences), Denmark (6.6%, 215 sequences) and the United States of America (6.3%, 208 sequences).

Globally, there has been a slow but steady increase in the proportion of BA.2.86 reported, with its global prevalence at 8.9% in epidemiological week 44, Table 1. This is a substantial rise from the data reported four weeks prior (week 40, 2 to 8 October 2023), when the global prevalence of BA.2.86 was 1.8% 

( Table 1: Global proportions of SARS-CoV-2 Variants, week 40 to week 44 of 2023)

*Table 2 below shows the BA.2.86 descendent lineages and the additional mutations relative to BA.2.86 in the spike and other proteins. A notable descendent lineage of BA.2.86 is JN.1 (BA.2.86 + S:L455S) with a global proportion of 3.2% in epidemiological week 44

 

As population immunity remains heterogenous globally due to differences in SARS-CoV-2 variants circulating around the world and in vaccination coverage, the immune escape potential of BA.2.86 will greatly depend on the immune background of the population tested. With this important caveat in mind, the immune escape of BA.2.86 relative to concurrently circulating variants appears to be limited, and certainly not as extensive as when Omicron emerged in the background of Delta (4-6). Sera from patients who had Omicron breakthrough infections (including XBB), exhibited robust neutralizing activity against BA.2.86, suggesting that upcoming XBB.1.5 monovalent vaccines could confer added protection, by triggering the expansion of existing B cells that will enhance cross-protection against BA.2.86 and its descendant lineages (7-8).
Importantly, T-cell memory has been reported to be highly durable and cross-reactive to BA.2.86 (9). This would suggest that there is sustained protection against severe disease caused by BA.2.86 infection as such protection is associated with T-cell memory (10). Initial observations of the reported BA.2.86 cases do not suggest a change in the clinical presentation or an increase in severity of this variant compared to other Omicron sublineages (11). 

Preliminary data from France also does not suggest differences with BA.2.86 in
terms of age, sex, symptoms or other risk factors (12).
WHO and its Technical Advisory Group on SARS-CoV-2 Evolution (TAG-VE) continue to recommend that Member States prioritize specific actions to better address uncertainties relating to antibody escape and severity of BA.2.86. The suggested timelines are estimates and will vary from one country to another based on national capacities:
• Share information on the growth advantage of BA.2.86 in your country and/or provide sequence
information (one to four weeks).
• Conduct neutralization assays using human sera, representative of the affected community(ies), and
BA.2.86 live virus isolates (two to four weeks).
• Perform a comparative evaluation to detect changes in rolling or ad hoc indicators of severity (four to
12 weeks).
The WHO and its Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC) continue to regularly assess the impact of variants on the performance of COVID-19 vaccines to inform decisions on updates to vaccine composition (2).

The risk evaluation below follows the WHO framework (13) and is based on currently available evidence. It will be revised regularly as more evidence and data from additional countries become available.

 

* Table1: BA.2.86 descendent lineages and mutations

Lineage
Variant Parent Lineage
Additional Spike Mutations relative to BA.2.86

Additional Mutations in other proteins relative to BA.2.86
BA.2.86        BA.2             NA           NA
BA.2.86.1     BA.2.86        None        ORF1a:K1973R
JN.1             BA.2.86.1     S:L455S  ORF1a:F499L, ORF1a:K1973R, ORF1a:R3821K, ORF7b:F19L
JN.2             BA.2.86.1    None         ORF1a:Y621C, ORF1a:K1973R
JN.3            BA.2.86.1     None         ORF1a:K1973R, ORF1a:T2087I
BA.2.86.2    BA.2.86       None         ORF7a:E22D
BA.2.86.3    BA.2.86      None           None
JQ.1            BA.2.86.3     S:T95I       ORF1a:D1742N