Uncertain rates of asymptomatic infections have raised concerns about potentially high rates of thus far undiagnosed SARS-CoV-2 infections. Serological testing for SARS-CoV-2 specific IgG can be helpful in identification of asymptomatic infections. We report baseline results of the CVOID-19 Contact (CoCo) Study, which follows 217 frontline healthcare workers at a university hospital and performs weekly SARS-CoV-2 specific serology (IgA/IgG). The majority of participants had direct contact to patients with infectious respiratory diseases. Study participants estimated their personal likelihood of having had a SARS-CoV-2 infection with a mean of 20.9% (range 0 to 90%). In contrast, anti-SARS-CoV-2-IgG prevalence was in the range of 1-2% among health care workers. The CoCo Study is not fully representative for other hospitals and the sensitivity of anti-SARS-CoV-2 serology in low prevalence conditions may require further improvement. Taken together, low rates of SARS-CoV-2 specific IgG in healthcare workers in Northern Germany are in sharp contrast to the high personal risk perception. Regular anti-SARS-CoV-2 IgG testing of health-care workers may aid in monitoring the pandemic, assessing the quality of immune responses, directing resources for protective measures, and assuring CVID-19 care in the long run.
Perceived versus proven SARS-CoV-2 specific immune responses in health care workers