Vaccines have been seen as the most important solution for ending the coronavirus disease 2019 (COVID‐19) pandemic. The aim of this study is to evaluate the antibody levels after inactivated virus vaccination. We included 148 healthcare workers (74 with prior COVID‐19 infection and 74 with not). They received two doses of inactivated virus vaccine (CoronaVac). Serum samples were prospectively collected three times (Days 0, 28, 56). We measured SARS‐CoV‐2 IgGsp antibodies quantitatively and neutralizing antibodies. After the first dose, antibody responses did not develop in 64.8% of the participants without prior COVID‐19 infection. All participants had developed antibody responses after the second dose. We observed that IgGsp antibody titers elicited by a single vaccine dose in participants with prior COVID‐19 infection were higher than after two doses of vaccine in participants without prior infection (geometric mean titer: 898 and 607 AU/ml). IgGsp antibodies, participants with prior COVID‐19 infection had higher antibody levels as geometric mean titers at all time points (p < 0.001). We also found a positive correlation between IgGsp antibody titers and neutralizing capacity (r_s = 0.697, p < 0.001). Although people without prior COVID‐19 infection should complete their vaccination protocol, the adequacy of a single dose of vaccine is still in question for individuals with prior COVID‐19. New methods are needed to measure the duration of protection of vaccines and their effectiveness against variants as the world is vaccinated. We believe quantitative IgGsp values may reflect the neutralization capacity of some vaccines.

Vaccination against SARS-CoV-2 may reduce COVID-19 mortality and complications in solidorgan transplant recipients, and we evaluated the associated antibody responses and adverse effects in this high-risk population. This prospective observational study (April-June 2021) included 10 liver and 38 kidney transplant recipients who received 2 vaccine doses (Sinovac, n = 31; or BioNTech, n = 17) and 56 healthy adults (Sinovac), all of whom provided 3 blood samples (prevaccination, 4 weeks after first dose, and 4-6 weeks after second dose) for quantitative tests (Abbott Quant assay forimmunoglobulin G antibodies against SARS-CoV-2 spike protein). Type I error was α = .05 in all statistical analyses (SPSS, version 25). We analyzed demographic data, antibody responses, and adverse events after 2 doses of SARSCoV-2 vaccine, comparedimmune responses from solidorgan transplant recipients (median age, 36.5 years) versus healthy patients (median age, 37.5 years), and observed significantly higher seropositivity in healthy versus transplant patients after Sinovac vaccination (100% vs 67.5%; P = .001). However, we observed no significant seropositive differences for Sinovac versus BioNTech second doses in transplantrecipients. Median SARS-CoV-2 immunoglobulin G level after second dose was significantly higher in BioNTech (1388.6 AU/mL) versus Sinovac patients (136.6 AU/mL) (P = .012). The seropositivity difference between the 2 vaccines was significant in participants 24 to 44 years old (P = .040). The rate of at least 1 side effect was 82.4% (n = 14) for BioNTech vaccine and 32.3% (n = 10) for Sinovac vaccine, and the difference was statistically significant.The most common side effect was arm pain (significantly higher in BioNTech group). Solid-organ transplant recipients demonstrated inadequate vaccine responses (higher risk of complications and mortality) versus healthy patients. Furthermore, immune responses may differ between vaccines. Therefore, additional vaccine doses and strict control measures remain crucial.

Objective: We aimed to investigate the vaccination status and the risk factors for the intensive care unit (ICU) support need of the laboratory-confirmed breakthrough COVID-19 infection inpatients. Materials and Methods: This multi-center point-prevalence study was conducted on inpatients, divided into two groups as ‘fully’ and ‘partially’ vaccinated according to COVID-19 vaccination status. Results: Totally 516 patients were included in the study. The median age was 65 (55-77), and 53.5% (n=276) of the patients were male. Hypertension (41.9%, n=216), diabetes mellitus (DM) (31.8%, n=164), and coronary artery disease (CAD) (16.3%, n=84) were the predominant comorbidities. Patients were divided into two groups ICU (n=196) and non-ICU (n=301). Hypertension (p=0.026), DM (p=0.048), and congestive heart failure (CHF) (p=0.005) were significantly higher in ICU patients and the median age was younger among non-ICU patients (p=0.033). Of patients, 16.9% (n=87) were fully vaccinated, and this group’s need for ICU support was statistically significantly lower (p=0.021). Conclusion: We conclude that older age, hypertension, DM, CHF, and being partially vaccinated were associated with the need for ICU support. Therefore, all countries should continuously monitor post-vaccination breakthrough COVID-19 infections to determine the national booster vaccine administration approach that will provide vulnerable individuals the highest protection. Keywords: COVID-19 vaccine, intensive care unit, risk factor, SARS-CoV-2 infection, vaccine breakthrough infections, variant of concerns

We evaluated neutralizing antibodies against the Omicron variant and Anti-Spike IgG response in solid organ (SOT) or hematopoietic stem cell (HSTC) recipients after a third dose of BNT162b2 (BNT) or CoronaVac (CV) following two doses of CV. In total, 95 participants underwent SOT (n = 62; 44 liver, 18 kidney) or HSCT (n = 27; 5 allogeneic, 22 autologous) were included from five centers in Turkey. The median time between third doses and serum sampling was 154 days (range between 15 to 381). The vaccine-induced antibody responses of both neutralizing antibodies and Anti-Spike IgGs were assessed by plaque neutralizing assay and immunoassay, respectively. Neutralizing antibody and Anti-Spike IgG levels were significantly higher in transplant patients receiving BNT compared to those receiving CV (Geometric mean (GMT):26.76 vs. 10.89; p = 0.03 and 2116 Au/mL vs. 172.1 Au/mL; p < 0.001). Solid organ transplantation recipients, particularly liver transplant recipients, showed lower antibody levels than HSCT recipients. Thus, among HSCT recipients, the GMT after BNT was 91.29 and it was 15.81 in the SOT group (p < 0.001). In SOT, antibody levels after BNT in kidney transplantation recipients were significantly higher than those in liver transplantation recipients (GMT: 48.32 vs. 11.72) (p < 0.001). Moreover, the neutralizing antibody levels after CV were very low (GMT: 10.81) in kidney transplantation recipients and below the detection limit (<10) in liver transplant recipients. This study highlights the superiority of BNT responses against Omicron as a third dose among transplant recipients after two doses of CV. The lack of neutralizing antibodies against Omicron after CV in liver transplant recipients should be taken into consideration, particularly in countries where inactivated vaccines are available in addition to mRNA vaccines.

Objective: Despite appropriate treatment and early diagnosis methods, Staphylococcus aureus bacteremia (SAB) is still associated with a high mortality rate. This study aims to evaluate the clinical features and approaches to SAB and to analyze the parameters that may affect 7-day and 30-day mortality. Materials and Methods: Adult patients with SAB data between 2011 and 2018 were evaluated retrospectively. Clinical data, patient demographics, and 7-day and 30-day mortality rates were obtained from their medical records. Results: In total, 144 patients were included in the study; 57.6% (83/144) of patients were men, and the mean age was 65.2±16.5 years. The most common source of infection was the central-line catheter (38.9%), followed by intra-abdominal (21%), respiratory (16.7), infective endocarditis (5.6%), and osteoarticular foci (2.1%). Fifteen percent (15%) of the strains were methicillin resistant. Transthoracic echocardiography (TTE) was performed for 80.6% (116/144) patients. Infectious diseases specialist consultation within 96 hours from blood culture signal was requested in 79.9%. Overall, 7-day mortality was 11.8%, and 30-day mortality was 21.5%. Staying in intensive care units (ICU) increased the risk of 30-day mortality by 1.1 times, and respiratory-focused SAB increased the risk by 4.3 times. Conclusion: SAB is still a big threat. Staphylococcal pneumonia remains a severe infection. Several prognostic factors influence mortality. Identifying the source, ensuring source control, and appropriate initial therapy as soon as possible are critical for reducing mortality and morbidity in SAB. Keywords: Staphylococcus aureus, bacteremia, staphylococcal pneumonia, mortality