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High Seroprevalence for SARS-CoV-2 Among Household Members of Essential Workers Detected Using a Dried Blood Spot Assay (WP-20-24)

Thomas McDade, Elizabeth McNally, Aaron Zelikovich, Richard D’Aquila, Brian Mustanski, Aaron Miller, Lauren Vaught, Nina Reiser, Elena Bogdanovic, Katherine Fallon, and Alexis Demonbreun

Objective: Serological testing is needed to investigate the extent of transmission of SARS-CoV-2 from front-line essential workers to their household members. However, the requirement for serum/plasma limits serological testing to clinical settings where it is feasible to collect and process venous blood. To address this problem the researchers developed a serological test for SARS-CoV-2 IgG antibodies that requires only a single drop of finger stick capillary whole blood, collected in the home and dried on filter paper (dried blood spot, DBS).

Methods: An ELISA to the receptor binding domain of the SARS-CoV-2 spike protein was optimized to quantify IgG antibodies in DBS. Samples were self-collected from a community sample of 232 participants enriched with health care workers, including 30 known COVID-19 cases and their household members.

Results: Among 30 individuals sharing a household with a virus-confirmed case of COVID-19, 80% were seropositive. Of 202 community individuals without prior confirmed acute COVID-19 diagnoses, 36% were seropositive. Of documented convalescent COVID-19 cases from the community, 29 of 30 (97%) were seropositive for IgG antibodies to the receptor binding domain.

Conclusion: DBS ELISA provides a minimally-invasive alternative to venous blood collection. Early analysis suggests a high rate of transmission among household members. High rates of seroconversion were also noted following recovery from infection. Serological testing for SARSCoV-2 IgG antibodies in DBS samples can facilitate seroprevalence assessment in community settings to address epidemiological questions, monitor duration of antibody responses, and assess if antibodies against the spike protein correlate with protection from reinfection.

Thomas McDade, Carlos Montezuma Professor of Anthropology and IPR Fellow, Northwestern University

Elizabeth McNally, Elizabeth J. Ward Professor of Genetic Medicine, Northwestern University

Aaron Zelikovich, Center for Genetic Medicine, Northwestern University

Richard D’Aquila, Howard Taylor Ricketts, MD, Professor of Medicine, Northwestern University

Brian Mustanski, Professor of Medical Social Sciences and IPR Associate, Northwestern University

Aaron Miller, Technical Director of Laboratory of Human Biology, Northwestern University

Lauren Vaught, Center for Genetic Medicine, Northwestern University

Nina Reiser, Center for Genetic Medicine, Northwestern University

Elena Bogdanovic, Postdoctoral Fellow, Center for Genetic Medicine, Northwestern University

Katherine Fallon, Center for Genetic Medicine, Northwestern University

Alexis Demonbreun, Assistant Professor of Pharmacology, Northwestern University

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