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Background: Monitoring SARS-CoV-2 seroprevalence dynamics during the COVID-19 pandemic is crucial for understanding population immunity and providing insights into public health policies. Limited data exist on this from Albania and other Eastern European countries. This study aimed to investigate SARS-CoV-2 seroprevalence in Albania, comparing August 2021 and August 2022 data from two representative samples of the general population. The objective was to understand the temporal dynamics of SARS-CoV-2 antibodies across age groups and assess the impacts of natural infection and vaccination on population immunity. Methods: This longitudinal study was conducted in two consecutive cross-sectional assessments 12 months apart in Albania's urban all-ages population. IgG anti-Spike-1 and anti-Nucleoprotein SARS-CoV-2 antibodies were measured using ELISA, focusing on seropositivity rates and antibody levels. Methods: The study encompassed 2143 and 2183 individuals in August 2021 and 2022, respectively, with the anti-S1-IgG seropositivity rate escalating from 70.9 ​% to 92.1 ​%. In 2021, seroprevalence ranged from 49.6 ​% (0–15 years) to 82 ​% (>60 years). By August 2022, it surpassed 90 ​% in most age groups, except 0–15 years (73.8 ​%). ''Hybrid'' immunity (COVID-19+ and Vaccine+) reached 56.6 ​% in 2022, or 2.8 times higher than in 2021, exhibiting the highest antibody levels compared to the only vaccinated or previously COVID-19-infected individuals. Conclusion: This study highlights an overall 94 % seroprevalence in the Albanian population in August 2022 and robust ''hybrid'' immunity, suggesting substantial protective immunity against SARS-CoV-2. The lower immunity in the 0–15 age group underscores the necessity for youth-targeted vaccine campaigns. These findings provide valuable insights for shaping healthcare measures and vaccination policies.

Background: This study aims to assess the changes in COVID-19 seroprevalence among the adult urban population of Albania between July and December 2020, when the Wuhan strain of SARS-CoV-2 virus was still prevalent in the country. Methods: Two independent, randomly selected samples of individuals aged 20–70 years residing in Metropolitan Tirana, Albania, were collected in June–July and December 2020. ELISA method was used for serological testing to determine IgG antibodies anti-S1-SARS-CoV-2. Results: The proportion of individuals classified as seropositive in early July was 7.5% (95% CI: 4.3%–10.7%), which increased 6.5 times in late December 2020, reaching 48.2% (95% CI: 44.8%–51.7%). The increasing seroprevalence rates in the study mirrored the trend of detected COVID-19 cases from June to December 2020 in Albania. However, they demonstrate a much higher cumulative incidence of the SARS-COV-2 infection in the community than the reported COVID-19 cases. Conclusion: The rapid increase in SARS-CoV-2 seroprevalence observed in Tirana City by the end of 2020 was likely a result of several factors, including the very low infection exposure between March–May 2020 when the entire city was in a lockdown, followed by the high susceptibility of the population due to naïve immunity. Despite the high observed seroprevalence at the end of December 2020, COVID-19 incidence continued to increase in Albania through 2021 and 2022 following the new virus variant surges.

Background: Histocompatibility testing (HT) which includes donor-recipient human leukocyte antigen (HLA) matching, cross-match testing (XMT) and anti-HLA antibody searching are crucial examinations in solid organ transplantation aiming to avoid the hyperacute graft rejection and also to predict the immunological outcome of the graft. Aims: The aim of this study was to analyse the tissue typing data collected at the Laboratory of Immunology and Histocompatibility of the University Hospital Center of Tirana, Albania, in order to define those actions that should be taken for improvements in the situation of kidney transplantation in Albania. Design: Descriptive study. Methods: The donor/recipient cross-match testing was performed through a standard complement-dependent cytotoxicity (CDC) assay using separated donor T and B cells that were tested in parallel with the recipient serum sample. All recipient sera were screened for anti-Class I and anti-Class II HLA antibodies using a bead based Luminex anti-HLA antibody screening test. In the case of detected positivity, an allele-specific anti-HLA antibody determination was conducted with the respective Luminex anti-Class I and Class II HLA antibody determination kits. Results: A total of 174 recipients and 202 donors were typed for the purpose of living donor kidney transplantation at our laboratory between January 2006 and December 2012. The mean age and female gender proportion of patients were 34.9 years and 34.5%, respectively, and 48.0 years and 65.3% for the donors, respectively. Here, 25.9% of the patients reported a positive complement-dependent cytotoxicity cross-match test and/or a positive anti-HLA antibody testing result. Eighteen patients that were negative for the complement-dependent cytotoxicity cross-match test were positive for anti-HLA antibodies. Conclusion: The predominant causes of end-stage renal disease (ESRD) in our patient population are chronic pyelonephritis and glomerulonephritis. The female gender is significantly more frequent among donors, which emphasises the need for more gender equity as far as the altruistic willingness for organ donation is concerned. The significant number of patients with Luminex anti-HLA antibody positivity combined with complement-dependent cytotoxicity cross-match negative results underlines the necessity of using additional methods like cell-based flow cytometry or bead-based Luminex anti-HLA antibody assays for the detection of anti-donor-specific antibodies. We also suggest that the number of kidney transplantations in Albania needs to be increased significantly by expanding it with paired exchange living donation and also by implementing an efficient deceased donor kidney transplantation program.