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Comparing dynamics and determinants of SARS-CoV-2 transmissions among health care workers of adult and pediatric settings in central Paris

Our take —

This study, available as a preprint and thus not yet peer reviewed, found that, of 13,278 healthcare workers from two hospital settings in Paris, 1,344 (10%) were symptomatic with potential COVID-19. Following testing, 373 (28%) tested positive for SARS-CoV-2 infection from February 24 to April 10, 2020, for an overall attack rate of 2.8% among healthcare workers. PPE use increased over the course of the study, and just over 60% (n=209/336, 62%) of infected healthcare workers reported using PPE always or almost always in the hospital. This study is likely affected by selection bias resulting in an underestimation of infection, given that only symptomatic workers were tested and provided additional information.

Study design

Prospective Cohort

Study population and setting

The objective of this study was to describe the disease dynamics and risk factors for SARS-CoV-2 infection among healthcare workers. Among 13,278 healthcare workers in two tertiary-care university hospitals in central Paris, including child and adult healthcare settings, 1,344 symptomatic healthcare workers were tested for SARS-CoV-2 from February 24 to April 10, 2020. Of these, 373 tested positive, and 336 (90%) responded to the phone interview to collect demographic and exposure information.

Summary of Main Findings

Among the 13,278 total healthcare workers, 1,344 were symptomatic (10%) and 373 (28%) of symptomatic workers tested positive. The overall estimated attack rate was 2.8%: in the adult setting, 251 (3.2%) of 7,916 healthcare workers tested positive with symptoms, and in the pediatric setting, 122 (2.3%) out of 5,362 tested positive with symptoms. The epidemic curve peaked on March 31, 2020, and then declined until the end of the study. Most positive and symptomatic workers were women (265, 79%), had patient-facing roles (234, 70%), and were not in COVID-19-specific wards (261, 78%). Over half of healthcare workers also reported wearing a mask always/most of the time at the hospital (141, 63% in adult setting, 68, 64% in children setting), and having >4 close contacts with colleagues per day without a mask (118, 52% in adult setting, 63, 59% in children setting). Outside of the hospital, the majority reported using public transportation (134, 59% in adult setting, 67, 62% in children setting), but the minority reported having a child in school or nursery outside the home, or wearing a mask outside the house. Over the course of the study, healthcare workers’ reported PPE use increased and leveled off, while close contact with a COVID-19 patient without PPE remained relatively stable

Study Strengths

This study had a large sample size of health workers, with data on their PPE practices and out-of-hospital exposure collected, which allows the study to assess trends over time, which were presented graphically. This out-of-hospital exposure data also included information on potential exposure from their children. Data is disaggregated by adult versus pediatric healthcare settings.


The study is limited by only testing symptomatic healthcare workers, thus underestimating positive cases because asymptomatic workers were not tested. They also did not assess potential exposure among non-cases, so they could not make comparisons whether certain exposure routes were more likely to lead to infection than others.

Value added

This is one of the largest studies of healthcare workers to date that includes information on potential exposure routes over a number of daily domains including mask-wearing, contact with other colleagues, use of public transport, and children in school/nursery.

This review was posted on: 25 June 2020