Neutralization and protective effectiveness of three XBB vaccines in older adults 12 months after booster

The durability of neutralizing antibodies following updated COVID-19 vaccination is a key determinant for optimizing booster strategies in older adults, who remain at high risk for severe outcomes because of immunosenescence and waning immunity. We previously reported neutralizing responses in a prospective cohort of 90 older adults (≥65 years) at 6 months after boosting with trivalent (Tri-XBB.1.5), bivalent (Bi-Omi-XBB), or tetravalent (Tetra-XBB.1) protein vaccines. 1 In this extended follow-up to 12 months post-vaccination of the same cohort, we assessed neutralizing antibody persistence, decay kinetics, and protective effectiveness against SARS-CoV-2 infection. Detailed methods are provided in the Supplementary Materials.