The emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2019 led to a global pandemic with far-reaching consequences for healthcare systems worldwide. Predisposing factors, such as immunosuppression and pre-existing medical conditions have been associated with an increased risk of severe disease. Healthcare workers represent a vulnerable cohort to SARS-CoV-2 infection due to a frequent contact to COVID-19 patients. Despite the availability of vaccines, such healthcare workers remain at a theoretically higher risk for infection as the vaccines available until the end of 2023 only insufficiently protected against SARS-CoV-2 variants such as Delta and Omicron BA.1 and BA.5.

In the present study, we evaluated the frequency of SARS-CoV-2 infections among healthcare workers with frequent contact to COVID-19 patients (high risk group), employees with contact to non-COVID-19 patients (intermediate risk group) and employees without any contact to SARS-CoV-2 (low risk group). We measured the cellular and humoral immune responses of healthcare workers considering their vaccination status and the number of prior infections. SARS-CoV-2 spike and nucleocapsid specific antibodies were determined by immunoglobulin ELISA. Neutralizing antibody titers were determined against SARS-CoV-2 variants D614G, Delta, Omicron BA.1 and BA.5. Cellular immune responses were assessed by an interferon-γ ELISpot.

Importantly, even three years post the onset of COVID-19 in Germany, healthcare workers engaged in nearly daily care of COVID-19 patients did not experience an elevated infection rate. Accordingly, there was no difference in the immune response between healthcare workers with daily contact with COVID-19 patients and employees without patient contact.

This observation underscores the effectiveness of existing hygiene standards in preventing patient-to-staff virus transmission.

The authors have nothing to disclose.