Humoral immunity induced by XEC monovalent vaccines against SARS-CoV-2 variants including XEC, LP.8.1, NB.1.8.1, XFG, and BA.3.2.

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Omicron variant has continuously diverged, and multiple of its sublineages are circulating worldwide. To reduce the coronavirus disease 2019 (COVID-19) with infection of the SARS-CoV-2 Omicron sublineages, some types of variant-matched vaccines have been developed and approved, such as Omicron JN.1-based vaccines and Omicron LP.8.1-based vaccines, in multiple countries, including Japan. Since, at the beginning of 2025, the Omicron XEC variant was predominant over other variants in Japan, two Japanese pharmaceutical companies have developed Omicron XEC-based vaccines. In this study, we evaluated the neutralizing antibody response induced by Omicron XEC-based vaccine and our data showed that both Omicron XEC-based vaccines can enhance the neutralizing titer of sera against a broad range of SARS-CoV-2 variants.