Background Serostudies are important resources when following pandemics and predicting their further spread, as well as determining the length of protection against reinfection and vaccine development. The aim of this study was to update data on the prevalence of seropositive individuals in Canton Sarajevo, Bosnia and Herzegovina (B&H) from September 2020 to May 2021. Methods Anti-SARS-CoV-2 antibodies were quantified using an electrochemiluminescence immunoassay. Results Compared to the period April–July 2020, when anti-SARS-CoV-2 antibodies were detected in 3.77% of samples, one year later (May 2021) the estimated percentage within the same population of the urban Canton Sarajevo was 29.9% (5,406/18,066). Of all anti-SARS-CoV-2 Ig-positive individuals, 53.27% were men, and 69.00% were of 50 years of age or younger. Also, the current update found the individuals 50 years of age or younger to be more frequently anti-SARS-CoV-2 Ig positive compared to older individuals. On the other hand, higher median anti-SARS-CoV-2 Ig levels were found in individuals > 50 years old than in younger individuals, as well as in men compared to women. Seropositivity gradually increased from September 2020 to May 2021, with the lowest frequency of positive cases (3.5%) observed in September 2020, and the highest frequency (77.7%) in January 2021. Conclusion Our results provided important seroprevalence data that could help in planning restrictive local public health measures to protect the population of Sarajevo Canton, especially considering that at the time of the study the vaccines were virtually inaccessible to the general population not belonging to any of the high-priority groups for vaccination.

IntroductionSerological detection of SARS-CoV-2-specific IgG and IgM antibodies is becoming increasingly important in management of COVID-19 pandemic.Material and methodsWe are reporting the first results of COVID-19 serological testing in Bosnia and Herzegovina on 2,841 samples collected and analyzed in two medical institutions in Sarajevo. Antibody detection was performed using commercially available kits.ResultsIn the first cohort, 43 IgM-positive/IgG-negative and 16 IgM-positive/IgG-positive individuals were detected, corresponding to 3.41% of participants having developed antibodies. In the second cohort, 4.28% participants were found to be IgM-negative/IgG-positive.ConclusionsOur results suggest need for population-wide serological surveying in B&H.

<p><strong>Objective</strong>. The aim of this study was to present data on the prevalence of seropositive children tested in the laboratory of the Eurofarm polyclinic in Sarajevo, from September 2020 to May 2021.</p><p><strong>Material and Methods</strong>. Peripheral blood samples were collected and anti-SARS-CoV-2 antibodies were detected using an electrochemiluminescence immunoassay.</p><p><strong>Results</strong>. In the total of 762 tested children, 187 were positive (24.5%), based on cut-off value. Of all the positive cases 42.8% were female while 57.2% were male. There were 10.1% of positive children in the first age group (0-5 years), 44.4% in the second group (6-13 years), and 45.5% in the third group (14-18 years). There was no statistically significant difference in seroprevalence between age groups and gender. The lowest seroprevalence (3.6%) was observed in October 2020 after the first pandemic wave, and the highest seroprevalence (60.3%) was observed in April 2021, corresponding to the third pandemic wave.</p><p><strong>Conclusion</strong>. The results of our study showed that the seroprevalence in children was low, especially during the first year of the pandemic. In the second year of the pandemic, there was an evident statistically significant increase in the number of seropositive children. Similar data have been shown in studies for adults.</p>