Abstract

Bulgaria, like many other countries, has experienced the far-reaching consequences of the Coronavirus disease 2019 (COVID-19) pandemic. Seroprevalence studies serve as a crucial method for assessing the exposure and immunity levels within a population. In this serosurvey, which is the first of this kind conducted in Bulgaria, we enrolled 104 healthcare workers (HCWs) from one front-line Bulgarian hospital and 237 individuals from the general population. Serum samples were collected in December 2021 from the general population and in February 2023 from HCWs and the general population. The presence of four anti-SARS-CoV-2 antibodies was evaluated: anti-Spike 1-IgG, anti-Nucleoprotein-IgG, anti-Spike1-IgA and anti-Recombinant binding domain neutralizing antibodies. Our results showed high percentages of seropositivity in both the HCWs and the general population (99% and 78%, respectively) in February 2023. HCWs had significantly higher mean IgA and mean anti-S1-IgG antibody levels compared to the general population. The seropositivity in the general population in December 2021 was 79%. The mean levels of IgA and anti-NCP-IgG were significantly higher, whereas the mean anti-S1-IgG levels were significantly lower in February 2023 compared to December 2021. We found a strong correlation between neutralizing antibodies and anti-S1-IgA and anti-S1-IgG antibodies for all tested groups. It is necessary to perform large-scale serosurveys to provide analysis of the seroprevalence in a larger population and its dynamics over time and to facilitate evidence-based strategies that will safeguard the health and well-being of the Bulgarian population and contribute to the global efforts in combating the COVID-19 pandemic.

摘要

与许多其他国家一样，保加利亚经历了 2019 年冠状病毒病 (COVID-19) 大流行的深远影响。血清阳性率研究是评估人群内暴露和免疫水平的重要方法。此次血清调查是在保加利亚进行的首次此类血清调查，我们招募了来自保加利亚一家一线医院的 104 名医护人员 (HCW) 和来自普通人群的 237 名个人。血清样本于 2021 年 12 月从普通人群中采集，并于 2023 年 2 月从医护人员和普通人群中采集。评估了四种抗 SARS-CoV-2 抗体的存在：抗 Spike 1-IgG、抗核蛋白-IgG、抗 Spike1-IgA 和抗重组结合域中和抗体。我们的结果显示，2023 年 2 月，医护人员和普通人群的血清阳性率都很高（分别为 99% 和 78%）。与普通人群相比，医护人员的平均 IgA 和平均抗 S1-IgG 抗体水平显着较高。2021 年 12 月，普通人群的血清阳性率为 79%。与 2021 年 12 月相比，2023 年 2 月 IgA 和抗 NCP-IgG 的平均水平显着升高，而平均抗 S1-IgG 水平显着降低。我们发现中和抗体与抗 S1-IgA 和抗 S1-IgG 之间存在很强的相关性。所有测试组的抗 S1-IgG 抗体。