Longitudinal determination of seroprevalence and immune response to SARS-CoV-2 in a population of food and retail workers through decentralized testing and transformation of ELISA datasets.

Publication date: Dec 16, 2024

Since the onset of the global COVID-19 pandemic in early 2020, numerous studies have been conducted worldwide to understand our immune response to the virus and to vaccination. This study investigates the humoral response elicited by SARS-CoV-2 infection and by vaccination in the poorly studied population of food and retail workers. These occupations were classified as essential by the Public Health Agency of Canada, potentially placing this population at greater risk of infection. Such a risk requires access to reliable and adaptable serological assays that can be rapidly deployed to guide public health strategies. Here we investigate the benefits and limitations of applying adaptable, decentralized tests for population-level immune surveillance in response to a pandemic, even before centralized testing is available. The 1. 5-year study period spans from early 2021, when vaccination became available in this region, to mid-2022, following the emergence of the first Omicron variants. The cohort of 304 food and retail workers was recruited in the QucE9bec City area. Participants attended five evenly spaced visits, providing blood samples as well as information on SARS-CoV-2 symptoms or risk factors, prior antigen or PCR test results and vaccination status, as well as work-related risk factors and protective measures. Parallel COVID-19 serological assays were performed using both a standardized chemiluminescent ELISA assay at the centralized platform operated in partnership with the Public Health Agency of Canada, and a semi-automated in-house colorimetric ELISA assay developed at our decentralized site. The YES/NO determination of SARS-CoV-2 vaccine seroconversion and/or infection events using the SARS-CoV-2 ancestral spike protein and nucleocapsid protein validated coherence of the centralized and decentralized assays. The flexibility of the decentralized assays allowed broadening the study to determine cross-reactivity of IgG directed against the spike protein of the SARS-CoV-2 Delta and Omicron VOCs, and IgM directed against the ancestral spike and nucleocapsid proteins. The nature of the data obtained in the decentralized assays allowed treatment with a recently developed mathematical transformation to obtain normal distribution, enabling ANOVA-Welsh statistical analysis. Although no significant differences were observed in humoral response as related to BMI, age, level of education, or chronic illnesses in this cohort of workers, statistically higher levels of vaccine-induced antibodies were observed for restaurant workers and hardware store workers in the early stages of the study, compared to workers in bars and grocery stores and in non-smokers versus smokers. This work highlights the importance of developing adaptable, decentralized tests for population-level immune surveillance in response to a pandemic, even before centralized testing is available. To our knowledge, no other study has reported such an extensive longitudinal investigation during key periods of the COVID-19 pandemic in a cohort of food and retail workers to analyze two types of immunoglobulin, three epitopes and antigens to three VOC. This study will inform strategies and measures to be implemented in the event of a future pandemic.

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Concepts Keywords
Canada Adult
Grocery Antibodies, Viral
Nucleocapsid Antibodies, Viral
Pandemic COVID-19
COVID-19 Serological Testing
Enzyme-Linked Immunosorbent Assay
Female
Humans
Immunoglobulin G
Immunoglobulin G
Longitudinal Studies
Male
Middle Aged
Quebec
SARS-CoV-2
Seroepidemiologic Studies

Semantics

Type Source Name
disease IDO immune response
disease MESH COVID-19 pandemic
pathway REACTOME SARS-CoV-2 Infection
disease MESH infection
disease IDO blood
disease IDO assay
disease IDO site
disease MESH seroconversion
disease IDO protein
disease MESH level of education
disease MESH chronic illnesses
drug DRUGBANK Diethylstilbestrol
disease MESH Inflammation
pathway REACTOME Reproduction
drug DRUGBANK Coenzyme M
drug DRUGBANK Hexocyclium
disease IDO production
disease MESH viral infections
disease IDO facility
disease IDO history
drug DRUGBANK Ademetionine
disease IDO host
disease IDO algorithm
drug DRUGBANK Hyaluronic acid
disease IDO humoral immune response
disease MESH overweight
disease MESH Reinfection
drug DRUGBANK Guanosine
disease MESH Infectious Diseases
disease MESH AIDS
disease IDO cell
disease MESH immunocompromised patients
disease MESH cancer
disease MESH clinical significance
disease MESH Sando
drug DRUGBANK Erythropoietin
disease IDO symptom
drug DRUGBANK (S)-Des-Me-Ampa

Original Article

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