High Seroprevalence of anti-SARS-CoV-2 antibodies among Ethiopian healthcare workers

BackgroundCOVID-19 pandemic has a devastating impact on the economies and health care system of sub-Saharan Africa. Healthcare workers (HWs), the main actors of the health system, are at higher-risk because of their occupation. Serology-based estimates of SARS-CoV-2 infection among HWs represent a measure of HWs exposure to the virus and a guide to the prevalence of SARS-CoV-2 in the community. This information is currently lacking in Ethiopia and other African countries. This study aimed to develop an in-house antibody testing assay, assess the prevalence of SARS-CoV-2 antibodies among Ethiopian high-risk frontline HWs. Methods and findingsA cross-sectional seroprevalence study was conducted among HWs in five public hospitals located in different geographic regions of Ethiopia. Socio-demographic and clinical data were collected using questionnaire-based interviews. From consenting HWs, blood samples were collected between December 2020 and February 2021, the period between the two peaks of COVID-19 in Ethiopia. The collected sera were tested using an in-house immunoglobin G (IgG) enzyme-linked immunosorbent assay (ELISA) for SARS-CoV-2 specific antibodies on sera collected from HWs. Of 1,997 HWs who provided a blood sample, demographic and clinical data, 50.5% were female, 74.0% had no symptoms compatible with COVID-19, and 29.0% had history of contact with suspected or confirmed patient with SARS-CoV-2 infection. The overall seroprevalence was 39.6%. The lowest (24.5%) and the highest (48.0%) seroprevalence rates were found in Hiwot Fana Specialized Hospital in Harar and ALERT Hospital in Addis Ababa, respectively. Of the 821 seropositive HWs, 224(27.3%) had history of symptoms consistent with COVID-19. A history of close contact with suspected/confirmed COVID-19 cases was strongly associated with seropositivity (Adjusted odds Ratio (AOR) =1.4, 95% CI 1.1-1.8; p=0.015). ConclusionHigh SARS-CoV-2 seroprevalence levels were observed in the five Ethiopian hospitals. These findings highlight the significant burden of asymptomatic infection in Ethiopia, and may reflect the scale of transmission in the general population. Author summaryO_ST_ABSWhy was this study done?C_ST_ABSO_LISevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a global public health threat, including Africa C_LIO_LIThe actual morbidity and mortality associated with SARS-CoV-2 infection in Ethiopia underestimated due to the limited molecular testing capacity. C_LIO_LIWe have limited knowledge about the seroprevalence of COVID-19 among health workers in Ethiopia. C_LIO_LIThis study aimed to develop an in-house immunoglobin G (IgG) enzyme-linked immunosorbent assay (ELISA) for SARS-CoV-2 specific antibodies on sera collected from HWs and to find out the proportion of healthcare workers who have developed antibodies specific to SARS-CoV-2 from five public hospitals located in the different regions of Ethiopia. C_LI What did the researchers do and find?O_LIA cross-sectional seroprevalence study was conducted among HWs in five public hospitals located in different geographic regions of Ethiopia. C_LIO_LISocio-demographic and clinical data were collected from recruited and consented participants using questionnaire-based interviews. C_LIO_LIBlood samples were collected from participants between December 2020 and February 2021, the period between the two peaks of COVID-19 in Ethiopia. C_LIO_LIThe collected sera were tested using an in-house ELISA for SARS-CoV-2 specific antibodies on sera collected from HWs. C_LIO_LIApproximately 40% of the 1,997 healthcare workers who participated in this study had antibodies against SARS-CoV-2 infection. C_LIO_LINo association between seropositivity and study participants age, gender, occupation, and comorbid medical conditions. C_LI What do these findings mean?O_LIThe observed high seroprevalence among healthcare workers regardless of their occupation suggests the cryptic but massive SARS-CoV-2 transmission in urban hospital settings. C_LIO_LIMost of the seropositive healthcare workers in the present study were asymptomatic, and might pose a threat to the most vulnerable populations such as individuals with comorbid medical conditions. C_LIO_LIGiven the low level of vaccine roll-out (1%), this study highlights the need to strengthen health workers adherence to personal protection practices such as wearing face masks to protect individuals at high risk of developing severe COVID-19 illness after SARS-CoV-2 infection. C_LI