Background: SARS-CoV-2 vaccines have shown high efficacy in protecting against COVID-19, although the determinants of vaccine effectiveness and breakthrough rates are yet to be determined. We aimed at investigating several factors affecting the SARS-CoV-2 IgG Spike (S) antibody responses on admission and clinical outcomes of COVID-19 disease in fully vaccinated, hospitalized patients. Methods: 102 subjects were enrolled in the study. Blood serum samples were collected from each patient upon admission for the semiquantitative determination of the SARS-CoV-2 IgG S levels with lateral flow assays. Factors influencing vaccine responses were documented. Results: 27 subjects had a negative antibody test upon hospital admission. Out of the 102 patients admitted to the hospital, 88 were discharged and 14 died. Both the absence of anti-S SARS-CoV-2 antibodies and poor clinical outcomes of COVID-19 disease were associated with older age, lower Ct values, and a shorter period between symptom onset and hospital admission. Ct values and time between symptom onset and hospitalization were independently associated with SARS-CoV-2 IgG S responses upon admission. The PaO2/FiO2 ratio was identified as an independent predictor of in-hospital mortality. Conclusions: Host- and disease-associated factors can predict SARS-CoV-2 IgG S responses and mortality in hospitalized patients with breakthrough SARS-CoV-2 Infection.

Background This study assessed the association between admission kidney function and the duration of hospitalization in triple-vaccinated coronavirus disease 2019 (COVID-19) inpatients during the omicron surge in Larissa, central Greece. Methods Regression analysis was used to estimate the effect of kidney function biomarkers on hospital length of stay (LoS) within a dataset from a cohort of 51 subjects. Results Sex- and age-adjusted admission serum creatinine was associated with hospital LoS (p=0.034). Conclusions Serum creatinine concentration on admission should be further evaluated as a possible clinical predictor of hospital LoS among triple-vaccinated COVID-19 inpatients both at the country and global level.

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