Guidelines for the use of respiratory personal protective equipment (PPE) to prevent the transmission of viral respiratory infectious diseases like COVID-19 in the hospital setting are based on limited evidence. In a network meta-analysis, researchers compared the protective effect of three types of respiratory PPE: N95 respirators, cloth masks, and surgical masks. They also compared continuous wearing (throughout a shift) with targeted wearing (only when performing high-risk procedures).

Six cluster randomized clinical trials with 12,265 health care workers were included in the analysis. As measured by the incidence of laboratory-confirmed viral respiratory infection, continuous wearing of an N95 respirator provided significantly better protection, compared with the control group. In terms of reducing the incidence of clinical respiratory illness, no intervention was significantly superior to the control group, although continuous wearing of an N95 respirator again scored highest. Surgical masks need to be replaced frequently and cloth masks provide only marginal protection.

The authors point out that because few studies about respiratory PPE have been published during the pandemic, the reliability of selection in their study is relatively lacking. They also note that their results are based largely on previous studies of other viral respiratory infections.