Randomized Controlled Trial to Compare Clinical Efficacy of Surgical and Filtering Facepiece 2 Masks for Care Home Workers Treating COVID-19 Patients

1. Project summary Recent results demonstrated an increased risk of COVID-19 infection among healthcare workers (HCW), particularly when access to personal protective equipment (PPE) was inadequate. (ref) During the COVID-19 pandemic, access to PPE has become complicated by a surge in worldwide demand combined with production limitations and logistical barriers. Since their introduction in hospitals in the 1990s, filtering facepiece (FFP) masks, mostly of the FFP2 type, are used by HCWs to protect themselves against bioaerosols due to tuberculosis, measles, and selected respiratory viruses. The COVID-19 pandemic has sparked debate around reasonable and safe use of the different types of face masks to protect the HCWs who provide direct care for COVID-19 patients. At the heart of the discussion is whether droplets or aerosols transmit SARS-CoV-2, and which of the two is responsible for what risk level of SARS-CoV-2 transmission resulting in disease.

The objective is to perform a cluster-randomized, parallel, controlled, non-inferiority study among Swiss nursing and retirement homes (homes) to evaluate the efficacy of surgical masks vs. FFP2 masks during patient care and prospectively observe possible infections amongst both vaccinated and unvaccinated staff.

Staff in nursing homes will be randomized to use either surgical or FFP2 masks for patient care consistently. Considering an attack rate of 0.8%[1] over three months among healthcare workers, a non-inferiority margin of 5%, and an intracluster variability of 0.01,[2] - we require a minimum of 625 participants per group.[3] The COVID-19 attack rate will be tested by initial serology testing and weekly pooled saliva specimen for SARS-CoV-2 testing. (Re)-Infections will be tracked by weekly pooled Saliva based PCR testing. Exposure to COVID-19 other than during work time will be explored by questionnaires and focus group discussions. 2. Study protocol 2.1 State of research in the field 2.1.1 Transmission of COVID-19 by droplets or aerosols Since the beginning of the COVID-19 pandemic, more than 110 million cases were confirmed with almost 2.4 million deaths as of February 22nd, 2020. Given that SARS-CoV-2 is a respiratory virus, its spread is expected to occur mainly by droplets (diameter >5µm) and via contact; however, laboratory tests suggest that SARS-CoV-2 may remain viable and infectious also in aerosols (diameter <5 µm).1,2. Both droplets and aerosols are naturally produced by humans when breathing, talking, coughing, or sneezing. A cough and a sneeze can generate between 3000 and 40,000 droplets of diameters between 0.5 to 12 µm, respectively 3-5; furthermore, droplets and aerosols can both contain SARS-CoV-2 virus if produced by COVID-19 patients. Aerosols are small-size droplets remaining in the air, and thus may travel beyond 2m from a source the respiratory tract bypassing surgical masks. Therefore, healthcare workers have been advised to wear FFP2 masks in procedures that generate aerosols. It remains to be clarified if surgical masks are inferior to FFP2 masks in the care of COVID-19 patients other than being exposed to aerosol-generating procedures. Recent data suggests that if worn correctly by both patient and exposed staff, surgical masks are able of filtering over 90% of particles generated 6.

Specifics about COVID-19 disease transmission and infectious dose are currently lacking. However, numbers in the order of 1000 droplets and more are realistic assumptions.7 The infection risk by one virus copy in viral shedding is about 1.5×10-6 to 1.6×10-5. Thus the infection risk due to aerosols at distances larger than 1-2 meters is substantially lower than that due to close interaction within 1 meter.

Consequently, protection from COVID-19 patients must focus on close interaction where droplets play a significant role, which could be addressed by wearing a surgical mask.