Abstract
Background:Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an ongoing global health crisis that has caused large scale morbidity and mortality. We aimed to determine the exposure to SARS-CoV-2 among young children and healthcare workers by measurement of anti-S1 antigen (spike protein) specific immunoglobulin G (IgG) using an in-house optimized indirect enzyme-linked immunosorbent assay (ELISA) method.Methods:Plasma samples were collected from cohorts of healthcare workers (n = 287) and young children aged from 6 weeks to 2 years old (n = 150) pre-COVID-19 pandemic between September 2018 and November 2019 and post-COVID-19 pandemic between August and December 2020 were simultaneously tested for anti-SARS-CoV-2 S1 specific IgG. The arithmetic mean of natural logarithm-transformed ELISA relative absorbance reading + (3 x standard deviation) of pre-pandemic plasma was used as the cut-off to determine SARS-CoV-2 IgG seropositivity of post-pandemic plasma.Results:There was no reactivity to SARS-CoV-2 S1 antigen detected in pre-pandemic plasma but in post pandemic plasma an 8.0% (23/287) IgG seropositivity in healthcare workers’ and 6.0% (9/150) seropositivity in children aged 2 years old was detected.Conclusions:Comparable levels of SARS-CoV-2 IgG seropositivity in healthcare workers and children suggest widespread exposure to SARS-CoV-2 in Zambia during the first wave of the pandemic. This finding has implications for continued acquisition and transmission of infection in the healthcare setting, household, and wider community.
Highlights
Coronavirus disease 2019 (COVID-19) caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an ongoing global public health emergency that as of April 2021 has infected more than 100 million people and claimed nearly three million lives worldwide1
Our objectives were to develop and optimize an in-house semi quantitative, indirect enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G (IgG) directed against SARS-CoV-2 spike glycoprotein (S1) and screen stored plasma samples from a cohort of healthcare workers and young children to permit estimation of SARS-CoV-2 seroprevalence within the healthcare setting and among young children residing in a peri urban community in Zambia
Included healthcare workers had a median age of 29 years, were mostly female 187/287 (65.2%), had normal body mass index 149/287 (51.9%) and were unmarried 145/287 (50.5%)
Summary
Coronavirus disease 2019 (COVID-19) caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an ongoing global public health emergency that as of April 2021 has infected more than 100 million people and claimed nearly three million lives worldwide. In the absence of mass SARS-CoV-2 nucleic acid testing for disease surveillance in lower income settings, the true extent of SARS-CoV-2 exposure within high-risk populations such as frontline healthcare workers and the wider population may be underestimated. In such settings, serology can serve as an important complementary diagnostic and surveillance tool. Methods: Plasma samples were collected from cohorts of healthcare workers (n = 287) and young children aged from 6 weeks to 2 years old (n = 150) pre-COVID-19 pandemic between September 2018 and November 2019 and post-COVID-19 pandemic between August and December 2020 were simultaneously tested for anti-SARS-CoV-2 S1 specific IgG. Conclusions: Comparable levels of SARS-CoV-2 IgG seropositivity in healthcare workers and children suggest widespread exposure to Invited Reviewers version 1
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