Evidence from SARS
China has considerable experience in dealing with SARS and COVID-19, so we additionally searched the Chinese Biomedicine Literature Database to find articles published in Chinese. Three case-control studies examining PPE and HWCs infection during the SARS outbreak 2002-2004 were found, These included 276 infected HCWs and 2099 non-infected HCWs.6-8 The most commonly used PPEs were masks, followed by gloves, protective clothing, and goggles.8These studies had similar findings that wearing any of: facemasks, gowns, gloves, goggles and footwear when caring for patients with SARS was associated with a lower risk of HCWs infection (P <0.05). The combination of different types of PPEs could reduce the risk of infection. In one study, 16/26 (61.5%) of HWP (involved in SARS patient contact) without PPE were infected, whereas none was infected when using all types of PPEs recommended by WHO.7 9
FFP2 face masks are similar to N95 face masks and both meet the WHO guidance for protection against COVID-19. FFP3 face masks, which are similar to N99 face masks, have a better filter performance based on the minimum filtration of 99%. All these four types of masks can block both liquid and solid aerosols.
N95 face masks, surgical face masks, cotton face masks and disposable face masks were all used by HCWs during SARS outbreak. Compared with those without facemasks, HCWs who wore more than 12-layer cotton masks had a lower risk of infection (OR 0.78, 95% CI 0.60-0.99).7 Two studies found that compared without wearing any masks, wearing simple paper face masks did not have a significantly protective effect.7 10 Ma et al (2004) also found that low-quality face masks (less than 12-layer cotton masks) were associated with a higher risk of infection (OR 76.68, 95% CI 16.74-351.31).6 Unsurprisingly, N95 facemasks, were the most efficacious in reducing HCW infection.11
Tight-fitting respirators (such as disposable FFP2 masks and reusable half masks) rely on having a good seal with the wearer’s face. ‘Fit testing’ is, therefore, a critical component to a respiratory protection program whenever HCWs use tight-fitting respirators. Additionally, tight-fitting respirators, including the N95, require a user seal check each time one is put on. In simulation studies, surgical masks had poor face fit and in vivo filtration efficiency compared with N95 masks and N99 masks.12 13