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