The COVID-19 pandemic has led to unprecedented demand for personal protective equipment. Shortages of surgical masks and filtering facepiece respirators has led to the extended use or re-use of single-use respirators and surgical masks by frontline healthcare workers, however the evidence base underpinning these practices is unclear. A number of national and international guidelines make reference to extended use, re-use and reprocessing of single-use masks and respirators1. We compared these guidelines first with each other and second with current synthesised evidence, particularly in the light of current worldwide shortages of personal protective equipment, in order to inform rapidly evolving policies and practice. The review was conducted in line with Cochrane rapid review interim guidance2.

IDENTIFICATION AND SYNTHESIS OF STUDIES
A targeted search of the World Health Organization, European Centre for Disease Prevention and Control, the US Centers for Disease Control and Prevention, and Public Health England websites was conducted to identify guidance. Four databases (Medline, Pubmed, Epistemonikos, Cochrane Database of Systematic Reviews) and three preprint repositories (Litcovid, MedRxiv and Open Science Framework) were searched for relevant systematic reviews. A full search strategy is provided below.

We defined extended use as the practice of using the same single-use mask or respirator for encounters with multiple patients, without removing it3. Re-use was defined as the practice of using the same mask or respirator for multiple encounters with patients, removing it (‘doffing’) for storage after each encounter and putting it on again (‘donning’) prior to the next encounter with a patient3. Reprocessing was defined as ‘decontamination using disinfection or sterilization methods followed by re-use of either reusable or disposable PPE’4. Record screening and data extraction was conducted by two reviewers. Quality of included systematic reviews was appraised by two reviewers using the AMSTAR-2 checklist. Findings were integrated and narratively synthesised.