The SARS-CoV-2 BA.2.86 variant is less immune evasive compared to FLip and other XBB variants, but more resistant to mAb S309. BA.2.86 shows higher fusogenicity and infectivity in CaLu-3 cells compared to 293T-ACE2 cells. The study compared the neutralization of BA.2.86 and FLip variants with sera from 3-dose-vaccinated and bivalent-vaccinated healthcare workers, XBB.1.5-wave-infected first responders, and monoclonal antibody S309. BA.2.86 is antigenically more similar to BA.2 and BA.4/5 than XBB variants. The fusion and infectivity of BA.2.86 is higher than XBB variants in CaLu-3 cells. The study highlights the importance of variant surveillance and the need for updated vaccines. The BA.2.86 variant has a D339H mutation that may prevent neutralization by S309. The study also shows that BA.2.86 has lower fusogenicity in 293T-ACE2 cells but higher in CaLu-3 cells, suggesting a different conformational stability of the spike. Molecular modeling revealed that mutations in BA.2.86 compromise S309 neutralization. The study underscores the need for updated vaccines and further research on the impact of BA.2.86 mutations on immune evasion and viral infectivity.The SARS-CoV-2 BA.2.86 variant is less immune evasive compared to FLip and other XBB variants, but more resistant to mAb S309. BA.2.86 shows higher fusogenicity and infectivity in CaLu-3 cells compared to 293T-ACE2 cells. The study compared the neutralization of BA.2.86 and FLip variants with sera from 3-dose-vaccinated and bivalent-vaccinated healthcare workers, XBB.1.5-wave-infected first responders, and monoclonal antibody S309. BA.2.86 is antigenically more similar to BA.2 and BA.4/5 than XBB variants. The fusion and infectivity of BA.2.86 is higher than XBB variants in CaLu-3 cells. The study highlights the importance of variant surveillance and the need for updated vaccines. The BA.2.86 variant has a D339H mutation that may prevent neutralization by S309. The study also shows that BA.2.86 has lower fusogenicity in 293T-ACE2 cells but higher in CaLu-3 cells, suggesting a different conformational stability of the spike. Molecular modeling revealed that mutations in BA.2.86 compromise S309 neutralization. The study underscores the need for updated vaccines and further research on the impact of BA.2.86 mutations on immune evasion and viral infectivity.