Abstract Objectives To assess neutralizing antibody responses to emerging SARS‐CoV‐2 variants Methods We explored SARS‐CoV‐2 neutralizing antibodies in140 adults participating in a longitudinal study of antibody responses to COVID vaccines. Participants reported monthly on vaccine doses, and SARS‐CoV‐2 infections. Serum was collected in December 2023 and April 2024 to determine neutralizing antibody to Wuhan ancestral strain and Omicron XBB.1.5 and JN.1 subvariants. Multivariate analysis assessed protective factors against a new SARS‐CoV‐2 infection between the two sampling times and 10 months follow up. Results 74% had hybrid immunity and 26% vaccine only immunity at study entry. A neutralizing antibody response was detected in 99% to Wuhan ancestral strain compared to 86% and 79% respectively to Omicron XBB.1.5 and JN.1 subvariants. For those with detectable antibodies the levels decayed, faster in those with vaccine only immunity and to the JN.1 subvariant. Neither the presence or the level of neutralizing antibody to JN.1 was associated with protection with a new SARS‐Cov‐2 infection over the 10‐month follow up period. Conclusion Neutralizing antibody levels to Omicron JN.1 subvariant were identified in 79% overall but in only 56% with vaccine only immunity. The presence or level was not associated with protection form a new SARS‐CoV‐2 infection over 10‐months. This data supports the development of pan‐coronavirus vaccine to expand protection against emerging variants.
Walmsley et al. (2026) studied this question.