Trend in SARS-CoV-2 Antibodies Seroprevalence in Bukavu Between 2020 and 2023: A Hospital-Based Retrospective Study

COVID-19 is undoubtedly underestimated in the South Kivu region due to the inaccessibility of reference diagnostic tests. In this context, serological tests could help estimate the disease’s circulation. This study analyzed the dynamics in the SARS-CoV-2 antibodies seroprevalence in Bukavu, East of the Democratic Republic of Congo.

The results of SARS-CoV-2 antibody tests performed in 2020 (n = 1100), 2021 (n = 508), and 2022-2023 (n = 246) in 4 clinics in Bukavu underwent analysis. Any subject, regardless of age, gender, and origin, was eligible for voluntary SARS-CoV-2 antibody screening. The screening was performed to determine the immune status for professional reasons or clinical clarification in symptomatic subjects. For this purpose, 4 mL of blood was obtained from an antecubital venipuncture for biological analysis. The data were also collected anonymously and confidentially. These rapid lateral flow immunoassays (Cellex qSARS-CoV-2 immunoglobulin G/M [IgG/IgM], and QuickZen COVID-19 IgM/IgG) detected and differentiated SARS-CoV-2 antibodies in volunteer workers and patients.

Between 2020 and 2023, the seroprevalence of SARS-CoV-2 antibodies (IgG + and IgM + ) increased from 37.9% to 65.4% (P < 0.0001). Early exposure to SARS-CoV-2 (IgM + /IgG-) increased significantly from 5.1% in 2020 to 11.4% in 2021, while it decreased significantly from 11.4% in 2021 to 4.5% in 2022-2023 (P < 0.0001). Full immunization (IgM-/IgG + ) increased from 2.5% in 2020 to 34.1% in 2022-2023. Age between 40 and 59 years (adjusted OR [95% CI]: 1.6 [1.3-2.1], P < 0.0001) and ≥ 60 years (adjusted OR [95% CI]: 1.6 [1.2-2.1], P = 0.001), as well as exposure periods 2021 (adjusted OR [95% CI]: 2.0 [1.6-2.5], P < 0.0001) and especially 2022-2023 (adjusted OR [95% CI]: 3.4 [2.5-4.7], P < 0.0001) remained independent predictors of SARS-CoV-2 antibody seroprevalence.

The findings of the present study demonstrated extremely high exposure to SARS-CoV-2 and full immunization of a significant proportion of the screened subjects. These results would explain the marginalization of new waves of COVID-19 in Bukavu despite low access to vaccination.