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

Abstract

Background COVID-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 could be used as a guide to the prevalence of SARS-CoV-2 in the community and valuable in combating COVID-19. 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 We developed and validated an in-house Enzyme-Linked Immunosorbent Assay (ELISA) for specific detection of anti-SARS-CoV-2 receptor binding domain immunoglobin G (IgG) antibodies. We then used this assay to assess the seroprevalence among HWs in five public hospitals located in different geographic regions of Ethiopia. From consenting HWs, blood samples were collected between December 2020 and February 2021, the period between the two peaks of COVID-19 in Ethiopia. Socio-demographic and clinical data were collected using questionnaire-based interviews. Descriptive statistics and bivariate and multivariate logistic regression were used to determine the overall and post-stratified seroprevalence and the association between seropositivity and potential risk factors. Results Our successfully developed in-house assay sensitivity was 100% in serum samples collected 2- weeks after the first onset of symptoms whereas its specificity in pre-COVID-19 pandemic sera was 97.7%. Using this assay, we analyzed a total of 1997 sera collected from HWs. Of 1997 HWs who provided a blood sample, and demographic and clinical data, 51.7% were females, 74.0% had no symptoms compatible with COVID-19, and 29.0% had a history of contact with suspected or confirmed patients 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%) of them had a history of symptoms consistent with COVID-19 while 436 (> 53%) of them had no contact with COVID-19 cases as well as no history of COVID-19 like symptoms. A history of close contact with suspected/confirmed COVID-19 cases is associated with seropositivity (Adjusted Odds Ratio (AOR) = 1.4, 95% CI 1.1–1.8; p = 0.015). Conclusion High 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.

Seroepidemiology of SARS-CoV-2 Virus in Healthcare Workers before Circulation of the Omicron Sublineages BA.4/BA.5 in Vojvodina, Serbia

“…However, a multiple logistic regression model found a significantly higher risk of seropositivity to SARS-CoV-2 in participants who had contact with COVID-19 patients at the workplace (frontliners who were directly involved in diagnosing, treating, and caring for COVID-19 patients), which strongly supports the notion that the differential risk of SARS-CoV-2 depends on the type of occupational exposure at the workplace. Similar results were found by other authors [19,23].…”

“…Thus, the seropositivity to SARS-CoV-2 may noticeably fluctuate depending on different parameters such as geographical location and the time when the research was conducted (stage of the pandemic), timeliness and the enforcement of infection control measures, the sampling strategies and type of serological test used, and may progressively increase over time. Therefore, it is not surprising that in our study, which was conducted later during the pandemic, after the sixth epidemic wave of COVID-19 and more than one year since the beginning of the vaccination campaigns in Serbia and elsewhere, the observed prevalence was much higher compared to the prevalence rates obtained in various populations of HCWs in several other SARS-CoV-2 seroprevalence studies that were performed before the period of our research [2,[16][17][18][19][20][21][22][23][24][25]. In addition, numerous previous studies reported that the seroprevalence to SARS-CoV-2 among HCWs was higher in comparison with the general population [4,17,26,27].…”

“…As already mentioned, seroprevalence research can identify the missing COVID-19 cases with mild or no symptoms at all, that were left undiagnosed [15,16,18,19]. Our previous study of four consecutive rounds of surveys in asymptomatic individuals from the general population showed marked differences in the numbers of infections estimated by the survey and the officially reported cases in Vojvodina and gave insight into the proportion of the susceptible population in a community (over 80% of the total population) after two pandemic waves [2].…”

A Single Dose of ChAdOx1 nCoV-19 Vaccine Elicits High Antibody Responses in Individuals with Prior SARS-CoV-2 Infection Comparable to That of Two-Dose-Vaccinated, SARS-CoV-2-Infection-Naïve Individuals: A Longitudinal Study in Ethiopian Health Workers

“…This procedure was performed to reduce risk from any potential virus in serum [19]. Detection of anti-RBD IgG antibodies in the sera was done using a validated in-house ELISA, as described previously [20]. To determine the end titer in seropositive serum samples, a two-fold serial dilution starting at 1: 200 in a 96-well ELISA plate was done.…”

The COVID-19 wave was already here: High seroprevalence of SARS-CoV-2 antibodies among staff and students in a Cameroon University

“…8 Given the difficulty and cost of RT-PCR based testing in resource-limited countries like Cameroon mildly affected or asymptomatic individuals are not usually screened, the number of confirmed SARS-CoV-2 infections is likely vastly underestimated. 9 In this context, seroprevalence surveys are of the most importance to assess the proportion of the population that have already developed antibodies following a previous exposure to SARS-CoV-2 and the immune responses to the virus. [10][11][12] The spike glycoprotein (S) and the nucleocapsid phosphoprotein (N) are the main viral antigenic targets against which antibodies are detected.…”