SARS-CoV-2 serological findings among employees in Oslo, Norway, by STAMI research group

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In the first wave of the coronavirus disease 2019 (COVID-19) pandemic, many countries enforced school closures. We enrolled 209 school and retail employees in Oslo, Norway to a cohort study after the first COVID-19 pandemic wave. Our aim was to characterize distribution of SARS-CoV-2 serology among employees; indirectly assessing those who had undergone a COVID-19 infection.

Exposure history, COVID-19-compatible symptoms and serum samples were collected at participating schools and warehouses in Oslo, Norway. SARS-CoV-2 antibodies targeting both the spikes and nucleocapsid of the virus were characterized by multiplex microsphere-based serological methods.

Preliminary data suggest, 3 % of the enrolled workers presented with positive SARS-CoV-2 serology, which was significantly higher than the expected 1 % prevalence in the general Oslo-population at this time-point (May-June 2020).  In school employees as a group, positive serology was not higher than expected (1 positive/96 negative), whereas positive serology in the retail employee group was significantly (P=0.005) higher than the expected 1 % (5 positive/107 negative). Comparing the two groups directly did not show significant differences due to a limited number of seropositives observed in both groups.

In conclusion, after the first wave and school closure of spring 2020, SARS-CoV-2 positive serology was not different from the anticipated 1 % among school workers, whereas it was higher than expected in a retail worker population (non-closure).

Presently, we are evaluating data on exposure risks. In addition, new samples from the cohort at follow-up, a half year after school reopening and passing of the second epidemiological wave, are being analyzed, and will shed light on the development of SARS-CoV-2 serology in these working populations.

More information
This cohort study was initiated in the early phases of the COVID-19 pandemic by the members of a research group at STAMI, and eventually financed by STAMI, to monitor the distribution of disease in two workers’ populations perceived as vulnerable.

Project group leader: Fred Haugen,

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