The state of Massachusetts was heavily impacted in the earliest stages of the pandemic, and a “super-spreader” event in the state in April 2020 may have seeded large case clusters throughout the country. Since emergence in early 2020, the SARS-CoV-2 virus has severely impacted the entire globe. No factors except geographic regions within the state were associated with evidence of prior SARS-CoV-2 infection in the secondary sampling group. In the primary sampling group, self-reported febrile illness since Feb 2020, male sex, and minority race (Black or American Indian/Alaskan Native) were associated with seropositivity. No association was found in either sample group between seropositivity and self-reported work duties or customer-facing hours. In the secondary sampling group, 10 (3.4%) of 292 individuals had IgG antibodies detected for an estimated adjusted prevalence of 4.0% (95% CI: 2.2 to 7.4). In the primary sample group, 36 (4.6%) had IgG antibodies detected for an estimated weighed prevalence for this population of 5.3% (95% CI: 3.5 to 8.0). Within the secondary sampling group of 214 individuals, 79 enrolled a household member. In the primary sampling group 548 returned samples, of which 230 enrolled a household member. Of the 1,001 individuals invited to participate in the study, 762 (76%) returned blood samples for analysis. Results Approximately 27,000 persons were invited via email to assess eligibility. Binomial models were used to assess factors associated with seropositivity in both sample groups separately. Seroprevalence estimates were adjusted for survey non-response. Samples were analyzed via ELISA for anti-SARS-CoV-2 IgG antibodies, and then IgM antibodies if IgG-positive.

After informed consent and a socio-behavioral survey, participants were mailed test kits and asked to return self-collected dried blood spot (DBS) samples. All staff, faculty, graduate students and librarians (secondary sampling group) were selected as a simple random sample.

Two separate sampling frames were generated from administrative lists: all undergraduates and their household members (primary sampling group) were randomly selected with probability proportional to population size. Methods Students, faculty, librarians and staff members at the University of Massachusetts, Amherst without a previous COVID-19 diagnosis were invited to participate in this study along with one member of their household in June 2020.

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