A total of 18 healthy individuals (15 female) with no history of SARS-CoV-2 infection at baseline who worked in the microbiology laboratory (out of 50 potential participants) served as controls. in controls (17/18, 94.4%). A booster effect was documented in post-vaccination samples of nursing-home residents with prior COVID-19. Plasma antibody levels were higher (p?Ednra strong TH1-skewed functional CD4+ and CD8+ T-cell responses in experimental models and humans [[1], [2], [3], [4]]. The efficacy of the vaccine has been shown to approach 95% in preventing COVID-19 across a wide range of age groups [5]. Real-world data have confirmed the efficacy of the vaccine in protecting against the occurrence of severe clinical forms of the disease [6,7]. Nevertheless, information on the immunogenicity and efficacy of this vaccine in elderly people with comorbidities and frailty is scarce [8,9]; such people have been prioritized for vaccination worldwide due to their increased risk of developing severe clinical forms of COVID-19 [10]. To gain further insight into this issue, we assess here SARS-CoV-2-S-targeted antibody and CPI-268456 functional T-cell responses after vaccination with Comirnaty in a cohort of nursing-home residents, most displaying one or more comorbidities, and either presumably SARS-CoV-2-na? ve or with documented prior SARS-CoV-2 infection. Material and methods Participants and study design CPI-268456 A total of 60 participants (44 female) in the study, selected from two nursing homes affiliated to the Clnico-Malvarrosa Health Department, Valencia, Spainwhich together provide care for 226 residentswere enrolled in the current study. A total of 18 healthy individuals (15 female) with no history of SARS-CoV-2 infection at baseline who worked in the microbiology laboratory (out of 50 potential participants) served as controls. Both patients and controls were randomly selected by creating an aleatory list using the Excel 2020 (Microsoft, Redmond, Washington, USA) INDEX function. Pre- and post-vaccination blood specimens from participants were collected in sodium heparin tubes (Beckton Dickinson, UK Ltd, UK). Informed consent was obtained from participants. The study was approved by the Hospital Clnico Universitario INCLIVA Research Ethics Committee (February, 2021). Antibody assays The following immunoassays were used in the current study. CPI-268456 (a) Roche Elecsys? Anti-SARS-CoV-2 S (Roche Diagnostics, Pleasanton, CA, USA), an electrochemiluminescence sandwich immunoassay (ECLIA) that quantifies total (IgG and IgM) antibodies directed against RBD. The assay is calibrated with the first WHO International Standard and Reference Panel for CPI-268456 anti-SARS-CoV-2 antibody [10]. (b) Elecsys? Anti-SARS-CoV-2 (Roche Diagnostics), a qualitative ECLIA detecting IgG and IgM antibodies against SARS-CoV-2 nucleoprotein. Both assays were run on cobas? e601 modular analyser (Roche Diagnostics, Rotkreuz, Switzerland). Plasma specimens were further diluted (1/10) for antibody quantification when appropriate. (c) LIAISON? SARS-CoV-2 TrimericS IgG assay (Diasorin S.p.A, Saluggia, Italy), run on a DiaSorin LIAISON platform (DiaSorin, Stillwater,.