COVID-19 Seroprevalence Test for IgG Antibody Levels Among Healthy Donors Across Different Pandemic Phases in Jeddah

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has significantly impacted global public health and the economy. This study aimed to investigate the seroprevalence of IgG antibodies against SARS-CoV-2 among healthy blood donors in Jeddah, Saudi Arabia, to better understand the dynamics of COVID-19 transmission during three distinct periods: pre-lockdown, during-lockdown, and post-lockdown. The seroprevalence was assessed concerning demographic factors such as gender, age, blood group, and nationality. A cross-sectional study was conducted from December 2019 to December 2020. A total of 3,825 blood samples from healthy donors were screened using an in-house enzyme-linked immunosorbent assay (ELISA) for anti-SARS-CoV-2 IgG antibodies detection. Positive samples were further confirmed using a micro-neutralization (MN) assay. Of 3,825 serum samples, 173 (4.5%) were tested positive by ELISA, and 147 samples were confirmed positive by MN. All samples collected before the lockdown (December 2019 to February 2020) were negative for IgG antibodies. During the lockdown period (March 2020 to June 2020), 44 out of 1,482 samples (2.97%) were tested positive. After the lockdown was eased (July 2020 to December 2020), the positivity rate increased to 12.15% (103 out of 848 samples). The overall seroprevalence rate among healthy blood donors was 3.84%, with significantly higher rates among non-Saudi and male donors (p = 0.00). The findings suggest that COVID-19 restrictions implemented by the Saudi authorities were effective in reducing the initial spread of the virus. However, the marked increase in seroprevalence over time suggests that asymptomatic or mildly symptomatic individuals may pose a significant risk for continued transmission. Continuous monitoring of seroprevalence is essential to control the spread of COVID-19.