Social mixing patterns of United States healthcare personnel at a quaternary health center: a prospective observational study.

Background: Understanding healthcare personnel's (HCP) contact patterns are important to mitigate healthcare-associated infectious disease transmission. Little is known about how HCP contact patterns change over time or during outbreaks such as the COVID-19 pandemic.

Methods: This study in a large United States healthcare system examined the social contact patterns of HCP via standardized social contact diaries. HCP were enrolled from October 2020 to June 2022. Participants completed monthly surveys of social contacts during a representative working day. In June 2022, participants completed a 2-day individual-level contact diary. Regression models estimated the association between contact rates and job type. We generated age-stratified contact matrices.

Results: Three-hundred and sixty HCP enrolled, 157 completed one or more monthly contact diaries and 88 completed the intensive 2-day diary. In the monthly contact diaries, the median daily contacts were 15 (interquartile range (IQR) 8-20), this increased slightly during the study (slope-estimate 0.004, p-value 0.016). For individual-level contact diaries, 88 HCP reported 2,550 contacts over 2 days. HCP were 2.8 times more likely to contact other HCP (n = 1,592 contacts) than patients (n = 570 contacts). Rehabilitation/transport staff, diagnostic imaging technologists, doctors, nurses, mid-level, and laboratory personnel had higher contacts compared with the lowest contact group (Nursing aids). Contact matrices concentrated in working-age populations.

Conclusions: HCP contacts concentrate in their work environment, primarily with other HCP. Their contacts remained stable over time even during large changes to societal contact patterns during the COVID-19 pandemic. This stability is critical for designing outbreak and pandemic responses.