The data are presented as median (minimummaximum)

The data are presented as median (minimummaximum). doses in our previous study. Antibody levels in venous blood serum were measured by the ECLIA method with the use of the Roche Cobas e411 analyzer. In all tested subjects, antibody titers remained high 10 months after vaccination, particularly in recovered COVID-19 patients, and only a minor decrease was observed relative to the values noted two months earlier. Keywords:BNT162b2, anti-SARS-CoV-2 antibodies, COVID-19, healthcare workers == 1. Introduction == An effective vaccine against the SARS-CoV-2 computer virus was eagerly anticipated ever since the outbreak of the global COVID-19 pandemic. The Pfizer/BioNTech BNT162b2 mRNA vaccine was the first preparation approved for use in late 2020. The vaccine contains mRNA encoding the spike (S) protein that is found on the surface of the SARS-CoV-2 computer virus, which enables the S protein to bind to the ACE-2 receptor and penetrate the host cells [1]. The efficacy of the Pfizer/BioNTech vaccine against symptomatic contamination with COVID-19 was initially estimated at 95% [1,2]. Both vaccines and natural infections elicit an immune response against the SARS-CoV-2 computer virus to protect the host organism. According to research, antibodies in the blood serum of recovered patients persist for at least three months after contamination, and this period is much longer after vaccination [3,4]. Several studies have exhibited that a history of COVID-19 contamination combined with two vaccine doses induces the strongest humoral immune response [5,6]. The efficacy of mRNA vaccines against the Delta [4] and Omicron [5] variants of SARS-CoV-2 has also been analyzed. Despite the fact that a full vaccination course provides considerable protection against infection, severe symptoms of COVID-19 and hospitalization, antibody levels decrease over time. New mutations of the virus have also emerged, and the global vaccination rate continues TSPAN3 to be low. In addition, the factors influencing the effectiveness of vaccines have not been fully elucidated. It is well known that demographic characteristics (age, gender, BMI) and chronic diseases may affect the level of antibodies [7,8,9]. As a result, the risk of reinfection with SARS-CoV-2 is high, which is why a booster dose of the COVID-19 vaccine has been introduced in many countries around the world to increase protection against the virus [10]. The vaccination program can be optimized by monitoring changes in anti-SARS-CoV-2S antibody levels over time in different population groups to determine titers that confer full protection against infection, and to identify groups where humoral immune responses to vaccination may be weaker [11]. The aim of the present study was to assess the anti-SARS-CoV-2S antibody levels in healthcare workers 10 months after the administration of two BNT162b2 vaccine doses, compare the results with the values obtained two months earlier (8 months after the full vaccination course), and investigate the demographic characteristics, comorbidities and previous COVID-19 infection that may potentially affect antibody titers. == 2. Materials and Methods == == 2.1. Materials == The population sample comprised 100 healthcare employees of the Hospital of the Ministry of Internal Affairs and Administration in Olsztyn. The analyzed subjects were aged 25 to 67 (mean 44, median 46), and the sample consisted of both males and females. The participants had been vaccinated with two doses of the BNT162B2 vaccine between 25 January and 17 February 2021. All participants gave their consent to participate in the NBD-557 study. The studied population was divided into two groups: vaccinated individuals with a history of SARS-CoV-2 infection that had been confirmed by the GeneXpert PCR assay (based on the detection of two target genes: E and N2) before the administration of two vaccine doses (4Q 2020) (n= 50), and vaccinated individuals without a history of SARS-CoV-2 infection (n= 50). Demographic data and information about comorbidities were collected from NBD-557 all participants. Each group was subdivided into subgroups based on gender (male, female), age (50, >50), type of work (medical, non-medical), BMI (24.9, >24.9), and presence of comorbidities in the past or at present, including NBD-557 diabetes, hypertension, cardiovascular diseases, autoimmune diseases, urinary tract diseases, hematological diseases and cancer (absent, present). Blood for antibody tests was sampled twice: 8 months and 10 months after the administration of two BNT162B2 vaccine doses. The blood was collected into red-top Vacutainer tubes for serum separation by centrifugation. The blood was centrifuged for 10 min at 4000gat room temperature. The serum was separated and frozen at 80 C until analysis. == 2.2. Method of Determining Antibody Levels ==.