A cluster randomised trial of cloth masks compared with medical masks in healthcare workers
A post-hoc analysis adjusted for compliance and other potential confounders showed that the rate of ILI was significantly higher in the cloth mask arm (RR=13.00, 95% CI 1.69 to 100.07), compared with the medical masks arm (
table 4). There was no significant difference between the medical mask and control arms.
Laboratory tests showed the penetration of particles through the cloth masks to be very high (97%) compared with medical masks (44%) (used in trial) and 3M 9320 N95 (<0.01%), 3M Vflex 9105 N95 (0.1%).
We have provided the first clinical efficacy data of cloth masks, which suggest HCWs should not use cloth masks as protection against respiratory infection. Cloth masks resulted in significantly higher rates of infection than medical masks, and also performed worse than the control arm.
The trend for all outcomes showed the lowest rates of infection in the medical mask group and the highest rates in the cloth mask arm.
The physical properties of a cloth mask, reuse, the frequency and effectiveness of cleaning, and increased moisture retention, may potentially increase the infection risk for HCWs.
We also showed that filtration was extremely poor (almost 0%) for the cloth masks. Observations during
SARS suggested double-masking and other practices increased the risk of infection because of moisture, liquid diffusion and pathogen retention.
31 These effects may be associated with cloth masks.
Further, we found no significant difference in rates of virus isolation in medical mask users between the three trials, suggesting that the results of this study could be interpreted as partly being explained by a detrimental effect of cloth masks.
This is further supported by the fact that the rate of virus isolation in the no-mask control group in the first Chinese RCT was 3.1%, which was not significantly different to the rates of virus isolation in the medical mask arms in any of the three trials including this one.
The data also show that the clinical case definition of ILI is non-specific, and captures a range of pathogens other than influenza. The study suggests medical masks may be protective, but the magnitude of difference raises the possibility that cloth masks cause an increase in infection risk in HCWs.
AGAIN, Cloth masks do nothing but make you at higher risk for illness. If everyone can have N95's, sure i get the mandate.