Risk mitigation of shared room ventilation and filtration on SARS-CoV-2 transmission: a multicenter test-negative study.

Background: Admission to shared hospital rooms are a risk factor of healthcare-associated (HA) SARS-CoV-2. Quantifying the impact of engineering controls such as ventilation and filtration is essential to informing resource utilization and infection prevention guidelines.

Methods: Multicenter test-negative study of patients exposed to SARS-CoV-2 in shared rooms across five hospitals between January and October, 2022. Independent variables tested were measured air changes per hour (ACH), presence of any room mechanical ventilation (RMV), or portable high-efficiency particulate air (HEPA) filter. Covariates included facility (number of beds in room, outbreak status of unit), source patient (presence of symptoms, RT-PCR cycle threshold (Ct) value), and exposed patient factors (age, sex, time from last SARS-CoV-2 vaccine, previous SARS-CoV-2 infection, exposure duration). Multilevel logistic mixed models used to estimate the impact of engineering controls on transmission.

Results: Among 468 exposed patients, secondary attack rate was 26.3% (range 7.5-33.3% across hospitals). In multivariable analysis, increased ACH was associated with decreased odds of infection (adjusted odds ratio (aOR) 0.88, 95% CI 0.78-1.00; p=.046) as were exposure duration and Ct value of source patient. Presence of RMV was also associated with decreased odds of infection (aOR 0.51, 95% CI 0.27-0.95; p=.034) while use of portable HEPA filter was not significant (aOR 0.58, 95% CI 0.26-1.31; p=.18).

Conclusions: Improved ventilation was independently associated with lower odds of SARS-CoV-2 infection among exposed roommates. Ensuring RMV is present and optimizing ACH may significantly mitigate the risk of HA-SARS-CoV-2. Future prospective studies should assess optimal ACH thresholds and the impact of portable HEPA filters.