JN.1 neutralizing antibody titers after XBB.1.5 monovalent vaccine boost in healthcare workers and people with HIV

Abstract

Winter 2023-2024 COVID-19 vaccine campaign will rely on the updated XBB.1.5-monovalent boost (with Moderna's mRNA-1273.815, Pfizer/ BioNtech's raxtozinameran, and Novavax' NVX-COV2601 having been recently approved). The in vitro efficacy of such vaccines against BA.2.86 has been demonstrated. 1,2 On November 22, 2023, WHO escalated BA.2.86 to a variant of interest (VOI) and on December 19, 2023 the direct descendant JN.1 was also classified as a separate VOI due to its rapid spread worldwide. The JN.1 VOI harbours the immune-escape Spike mutations L455F, 3,4 similarly to the L455F in "FLip" sublineages. 5,6 We report here JN.1-neutralizing antibody (nAb) titers in 14 healthcare workers (HCW) and 11 people with HIV (PWH) attending the National Institute for Infectious Diseases Lazzaro Spallanzani in Rome who received a dose of the updated messenger RNA (mRNA) monovalent vaccine (raxtozinameran) in October 2023. Samples were collected on the day of vaccination (T0) and 1 month later (T1) (median 31 days, interquartile range [IQR]: 29-35) after the raxtozinameran vaccine. Live authentic JN.1 and XBB.1.16 cultured on Vero E6 cells were used for the micro-neutralization assays. The highest serum dilution inhibiting at least LETTER TO THE EDITOR Committee of the Lazzaro Spallanzani Institute (approval number: 423/2021; amendment adopted with no. 91/2022). The participants included in the present study provided informed written consent.