Effect of Universal Masking on Non-Severe Acute Respiratory Syndrome Coronavirus 2 Healthcare-Associated Respiratory Viral Infections.

Background: Respiratory viral infections are common and are a major cause of morbidity and mortality. We evaluated the impact of universal masking implemented during the coronavirus disease 2019 (COVID-19) pandemic on other healthcare-associated respiratory viral infections (HA-RIs) in an academic medical center.

Methods: A retrospective cohort study was performed among all inpatients aged ≥18 years admitted between 1 May 2019 and 30 June 2022. Universal masking was implemented in May 2020 at our hospital and state-level mask mandates had been lifted by May 2021. We evaluated and compared the HA-RI rates, adjusted for monthly community-onset viral infections, during the premasking period, universal masking period, and post-community mandate period.

Results: We identified 3015 patients (median age, 58 years; 48.0% males) with a positive respiratory viral test within 14 days prior to, or during, their hospitalization; 441 (14.6%) patients had an HA-RI. Rhinovirus/enterovirus (51.0%), parainfluenza virus (14.3%), coronaviruses (229E, OC43, HKU1, and NL63; 13.2%) and influenza (10.0%) were the predominant HA-RI viruses detected. The monthly HA-RI rate decreased 34.9% (95% confidence interval, 8.8%-51.8%) after the implementation of universal masking (0.71 premasking period vs 0.19 universal masking period vs 0.35 infections per 1000 patient-days in the post-community mandate period) while accounting for a drop in the community-onset respiratory viral infections using a structural time-series model analysis ( < .001), with no significant change in HA-RI rates with the relaxation of community masking mandate.

Conclusions: Implementation of universal masking at our hospital was associated with a significantly reduced incidence of HA-RIs.