facemask [25]. In addition, the efficiency filtration rate of facemasks is poor, ranging from 0.7%
in non-surgical, cotton-gauze woven mask to 26% in cotton sweeter material [2]. With respect to
surgical and N95 medical facemasks, the efficiency filtration rate falls to 15% and 58%,
respectively when even small gap between the mask and the face exists [25].
Clinical scientific evidence challenges further the efficacy of facemasks to block human-tohuman transmission or infectivity. A randomized controlled trial (RCT) of 246 participants [123
(50%) symptomatic)] who were allocated to either wearing or not wearing surgical facemask,
assessing viruses transmission including coronavirus [26]. The results of this study showed that
among symptomatic individuals (those with fever, cough, sore throat, runny nose ect…) there
was no difference between wearing and not wearing facemask for coronavirus droplets
transmission of particles of >5 µm. Among asymptomatic individuals, there was no droplets or
aerosols coronavirus detected from any participant with or without the mask, suggesting that
asymptomatic individuals do not transmit or infect other people [26]. This was further supported
by a study on infectivity where 445 asymptomatic individuals were exposed to asymptomatic
SARS-CoV-2 carrier (been positive for SARS-CoV-2) using close contact (shared quarantine
space) for a median of 4 to 5 days. The study found that none of the 445 individuals was
infected with SARS-CoV-2 confirmed by real-time reverse transcription polymerase [27].
A meta-analysis among health care workers found that compared to no masks, surgical mask
and N95 respirators were not effective against transmission of viral infections or influenza-like
illness based on six RCTs [28]. Using separate analysis of 23 observational studies, this metaanalysis found no protective effect of medical mask or N95 respirators against SARS virus [28].
A recent systematic review of 39 studies including 33,867 participants in community settings
(self-report illness), found no difference between N95 respirators versus surgical masks and
surgical mask versus no masks in the risk for developing influenza or influenza-like illness,
suggesting their ineffectiveness of blocking viral transmissions in community settings [29].
Another meta-analysis of 44 non-RCT studies (n = 25,697 participants) examining the potential
risk reduction of facemasks against SARS, middle east respiratory syndrome (MERS) and
COVID-19 transmissions [30]. The meta-analysis included four specific studies on COVID-19
transmission (5,929 participants, primarily health-care workers used N95 masks). Although the
overall findings showed reduced risk of virus transmission with facemasks, the analysis had
severe limitations to draw conclusions. One of the four COVID-19 studies had zero infected
cases in both arms, and was excluded from meta-analytic calculation. Other two COVID-19
studies had unadjusted models, and were also excluded from the overall analysis. The metaanalytic results were based on only one COVID-19, one MERS and 8 SARS studies, resulting in
high selection bias of the studies and contamination of the results between different viruses.
Based on four COVID-19 studies, the meta-analysis failed to demonstrate risk reduction of
facemasks for COVID-19 transmission, where the authors reported that the results of metaanalysis have low certainty and are inconclusive [30].
In early publication the WHO stated that “facemasks are not required, as no evidence is
available on its usefulness to protect non-sick persons” [14]. In the same publication, the WHO
declared that “cloth (e.g. cotton or gauze) masks are not recommended under any
circumstance” [14]. Conversely, in later publication the WHO stated that the usage of fabricmade facemasks (Polypropylene, Cotton, Polyester, Cellulose, Gauze and Silk) is a general
community practice for “preventing the infected wearer transmitting the virus to others and/or to
offer protection to the healthy wearer against infection (prevention)” [2]. The same publication
further conflicted itself by stating that due to the lower filtration, breathability and overall
performance of fabric facemasks, the usage of woven fabric mask such as cloth, and/or nonwoven fabrics, should only be considered for infected persons and not for prevention practice in
asymptomatic individuals [2]. The Central for Disease Control and Prevention (CDC) made
similar recommendation, stating that only symptomatic persons should consider wearing
facemask, while for asymptomatic individuals this practice is not recommended [31]. Consistent
with the CDC, clinical scientists from Departments of Infectious Diseases and Microbiology in
Australia counsel against facemasks usage for health-care workers, arguing that there is no
justification for such practice while normal caring relationship between patients and medical
staff could be compromised [32]. Moreover, the WHO repeatedly announced that “at present,

3