Viral load dynamics in healthcare workers with COVID-19 during Delta and Omicron era

Abstract During the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, several variants of concern (VOC) have emerged and became the dominant strain. These are considered VOC because of traits like increased transmissibility, increased severity, and immune-evasion. Understanding their viral load dynamics, with the use of longitudinal follow-up data, can help to understand transmission and could inform policy makers on for example infection prevention guidelines. However, longitudinal follow-up studies are scarce. In this study, we were able to monitor the viral load dynamics of the Delta, Omicron BA.1 and BA.2 variants via an unique dataset that was obtained as a consequence of the implemented infection prevention guidelines for healthcare workers at our institution, based on longitudinal follow-up of viral load. We found that the dynamics are different between Delta, Omicron BA.1, and Omicron BA.2 variants, the latter having the highest viral load on day 5 (5.7 log10 copies/mL compared to 4.3 log10 copies/mL for Delta and 4.8 log10 copies/mL for BA.1) and day 7 (4.4 log10 copies/mL compared to 3.3 log10 copies/mL for Delta and 3.8 log10 copies/mL for BA.1). However, the infection duration does not appear to be different between these variants. Still, considerable viral loads even after the suggested quarantine period were observed, in particular for the Omicron BA.2 sub variant. This highlights the need for a tailored approach per variant as results of previously circulating variants do not always match. This is in particular important for healthcare workers as they can transmit SARS-CoV-2 to vulnerable patients.