Sensitivity of the SARS-CoV-2 BA.2.86 variant to prevailing neutralising antibody responses

After a prolonged period of near-complete global dominance of the recombinant XBB family of SARS-CoV-2 lineages, a substantially mutated sublineage of BA.2 has recently emerged. With a long branch of unobserved evolution (figure A), including more than 30 mutations in the spike protein relative to BA.2, with many at key antigenic sites (figure B), the emergence of BA.2.86 is reminiscent of the initial emergence of omicron.2 This raises immediate questions about whether it is sensitive to any previously approved clinical monoclonal antibodies with activity against BA.2, and the degree to which it is able to escape antibody responses in the current setting in which individual exposure histories are a complex combination of multiple immunisations and multiple previous SARS-CoV-2 infections. To characterise the relative sensitivity of BA.2.86 to current antibody-mediated immunity at the population level, we evaluated BA.2.86 neutralisation by serum sampled from random blood donors in Stockholm, Sweden, during week 34 (Aug 21–27), 2023.