SARS-CoV-2 vaccination has reduced hospitalization and mortality for nursing home residents (NHRs) but emerging variants and waning immunity challenge vaccine effectiveness. This study assesses the immunogenicity of the most recent XBB.1.5 monovalent vaccine to variant strains among NHRs. Participants were subset of a longitudinal study of consented NHRs and Healthcare workers (HCWs) who have received serial blood draws to assess immunogenicity with each SARS-CoV-2 mRNA vaccine dose. We report data on participants who received the XBB.1.5 monovalent vaccine post-FDA approval in Fall 2023. NHRs were categorized by whether they had an interval SARS-CoV-2 infection between their first bivalent vaccine dose and their XBB.1.5 monovalent vaccination. The sample included 61 NHRs [median age 76 (IQR 68–86), 51% female] and 28 HCWs [median age 45 (IQR 31–58), 46% female). After XBB.1.5 vaccination, a robust geometric mean fold rise (GMFR) in XBB.1.5-specific neutralizing antibody titers was observed:17.3 (95% confidence interval [CI] 9.3, 32.4) and NHRs with interval infection and 11.3 (95% CI 5, 25.4) in those without and 13.6 (95% CI 8.4,22) in HCWs. For JN.1-specific titers, GMFRs were 14.9 (95% CI 7.9, 28) and 6.5 (95% CI 3.3, 13.1) in NHRs with and without interval infection, and 11.4 (95% CI 6.2, 20.9) in HCWs. NHRs with interval SARS-CoV-2 infection had higher titers across all analyzed strains analyzed. The XBB.1.5 vaccine significantly elevates Omicron-specific neutralizing antibody titers to XBB.1.5 and JN.1 strains in both NHRs and HCWs with more pronounced in those previously infected with SARS-CoV-2 since bivalent vaccination.

SARS-CoV-2 疫苗接种降低了疗养院居民 （NHR） 的住院率和死亡率，但新出现的变种和免疫力的减弱对疫苗的有效性提出了挑战。本研究评估了最新的 XBB.1.5 单价疫苗对 NHR 中变异毒株的免疫原性。参与者是同意的 NHR 和医护人员 （HCW） 的纵向研究的子集，他们接受了连续抽血，以评估每剂 SARS-CoV-2 mRNA 疫苗的免疫原性。我们报告了 2023 年秋季 FDA 批准后接受 XBB.1.5 单价疫苗的参与者的数据。NHR 根据他们在第一剂二价疫苗和 XBB.1.5 单价疫苗接种之间是否间隔感染 SARS-CoV-2 进行分类。样本包括 61 名 NHR [中位年龄 76 岁（IQR 68-86），51% 女性] 和 28 名 HCW [中位年龄 45 岁（IQR 31-58），46% 女性）。接种 XBB.1.5 疫苗后，观察到 XBB.1.5 特异性中和抗体滴度的稳健几何平均倍数上升 （GMFR）：17.3（95% 置信区间 [CI] 9.3,32.4）和间隔感染的 NHR，11.3（95% CI 5,25.4）在未感染的患者中为 13.6（95% CI 8.4,22）在 HCW 中。对于 JN.1 特异性滴度，GMFR 分别为 14.9（95% CI 7.9、28）和 6.5（95% CI 3.3， 13.1） 在有和没有间隔感染的 NHR 中，在 HCW 中为 11.4 （95% CI 6.2， 20.9）。间隔 SARS-CoV-2 感染的 NHR 在所有分析的菌株中具有更高的滴度。XBB.1.5 疫苗在 NHR 和 HCW 中显着提高了 Omicron 特异性中和抗体滴度到 XBB.1.5 和 JN.1 毒株，在二价疫苗接种后先前感染过 SARS-CoV-2 的人群中更为明显。