A recent study published by the Cambridge University Press (25/9/23) showed that when a hospital replaced the requirement for universal masking of all healthcare personnel and visitors in all clinical buildings with a requirement for masking only during patient encounters, an immediate, substantial, and sustained increase in healthcare-associated respiratory viral infections was observed.
Prior to the pandemic, the baseline HARVI rate was 7.07 per 10,000 patient days. With pandemic masking and testing policies, this declined to 2.60. In late 2021, as masking relaxed and omicron emerged, HARVIs increased back to the baseline rate. When universal masking ended in November 2022, HARVIs sharply increased further to 12.88 per 10,000 patient days.
From November 2022 to June 2023, there were increases in rhinovirus/enterovirus, parainfluenza, adenovirus, SARS-CoV-2, endemic coronaviruses, influenza A, metapneumovirus, and RSV. The median time from admission to infection was 24.5 days, similar to prior periods.
The increase in HARVIs occurred despite no other infection prevention changes, low COVID-19 admissions, and declining community respiratory virus rates. The earlier increase with relaxation of policies provides additional evidence that masking and other mitigation strategies reduced transmission.
In summary, discontinuation of universal masking was associated with a significant and sustained increase in HARVIs, suggesting it was an effective strategy. Universal masking should be considered to reduce healthcare-associated respiratory virus transmission.
The full report can be read online here.