Viral whole-genome sequencing to assess impact of universal masking on SARS-CoV-2 transmission among pediatric healthcare workers.

ABSTRACT

OBJECTIVE: To identify the impact of universal masking on COVID-19 incidence and putative SARS-CoV-2 transmissions events among children's hospital healthcare workers (HCWs). DESIGN: Quasi-experimental study. SETTING: Single academic free-standing children's hospital. METHODS: We performed whole-genome sequencing of SARS-CoV-2- PCR-positive samples collected from HCWs 3 weeks before and 6 weeks after implementing a universal masking policy. Phylogenetic analyses were performed to identify clusters of clonally related SARS-CoV-2 indicative of putative transmission events. We measured COVID-19 incidence, SARS-CoV-2 test positivity rates, and frequency of putative transmission events before and after the masking policy was implemented. RESULTS: HCW COVID-19 incidence and test positivity declined from 14.3 to 4.3 cases per week, and from 18.4% to 9.0%, respectively. Putative transmission events were only identified prior to universal masking. CONCLUSIONS: A universal masking policy was associated with reductions in HCW COVID-19 infections and occupational acquisition of SARS-CoV-2.