What do medical face masks do for COVID-19?

       Are masks more effective than vaccination in preventing COVID-19 infection? This is the meaning of a new public service announcement issued by the Centers for Disease Control and Prevention (CDC), which was headed by Rochelle Walensky, the director of the agency.
       ”The evidence is clear,” Varensky said in a 37-second video posted on Twitter last Friday. “Masks can help prevent the spread of COVID-19, reducing your chances of infection by more than 80%, whether it’s flu, coronavirus, or even just the common cold. Combine with other steps, such as getting vaccinated, washing your hands, and keeping your distance , Wearing a mask is an important step to keep all of us healthy.”
       If wearing a mask reduces the risk of infection by “over 80%,” as Walensky seems to be saying, this protective measure will be very effective. This risk reduction will be higher than the effective rate found in several real-world studies of mRNA vaccines. In six studies conducted when the delta variant was dominant, vaccination and infection reduction ranged from 54% to 85%. Five of these studies had an effective rate of 80% or less, although the reduction in symptomatic cases, severe illness, and hospitalization was greater (keep this in mind when assessing the benefits of vaccination).
       What is the source of Varensky’s surprising claim that masks are better at preventing infections than vaccines? I asked the CDC, but I haven’t received a response yet. * However, based on the CDC’s summary of the evidence supporting wearing masks, Walensky relied on a laboratory study published in the journal Science Advances last September.
       The researchers used cameras to record the respiratory droplets irradiated by lasers from speakers wearing 14 masks, from N95 respirators and surgical masks to headscarves and neck guards. The valveless N95 mask is 99.9% effective in retaining “droplet sizes greater than 0.5 microns” (estimated detection limit), and neck leggings seem to be worse than useless, apparently because it breaks up larger droplets Into smaller droplets. Between the two, three-layer surgical masks and several other cloth masks reduced the number of droplets detected by more than 80%. Based on these results, the CDC concluded: “In human experiments that measure all respiratory droplet obstructions, more than 80% of obstructions have been achieved.”
       Although this gloss is a bit misleading considering the detection limit pointed out by the researchers, it is a far cry from Walensky’s assertion that the mask “reduces your chance of infection by more than 80%.” It is fair to use this study as evidence that masks can help reduce the risk of COVID-19 transmission. But Varensky is doing much more than that: She is trying to quantify the impact of masks on the real world based on a laboratory study that did not measure them.
       There are several reasons to be wary of such conclusions, including the gap between stylized laboratory conditions and chaotic reality. In this study, a person wearing a mask spoke through a hole in a box. He recited the phrase “keep healthy, people”, but he did not cough, sneeze, yell, or sing. Masks are clean and worn properly, which is not always true in real life. Although the study found that the type of cloth mask has an important influence on its performance, Varensky’s information implicitly assumes that everyone will choose the most effective model.
       To make matters worse, Walensky’s ambiguous statement may be interpreted as meaning that people wearing masks have therefore reduced their risk of contracting COVID-19 by “over 80%.” Varensky reinforced this impression in her tweet, saying that “wearing a mask” will help you “keep healthy.” The study looked at droplets emitted by mask wearers, but did not provide a basis for this claim.
       At the same time, Walenksy’s tweet seems to confirm her estimate, saying that “masks can help you reduce the chance of #COVID19 infection by more than 80%” (emphasis added). Assuming you are also vaccinated, even if the mask is far less effective than what Varensky said in the video, this may be true.
       In view of the gap between the research and Varensky’s interpretation, she should completely avoid the erroneous accuracy of the number “over 80%”. You might think that a public health official who has repeatedly been criticized for misrepresenting COVID-19 research will learn to be more careful when presenting scientific findings to the public. Valensky’s mask exaggeration not only further weakens her credibility; it implicitly makes masking look better than vaccination, as a tool to avoid COVID-19 and prevent its spread, which is hardly beneficial to the public Health information.
       *Update, November 10: I received a response from the CDC today, which did not cite any specific research to support Walensky’s statement. This email may or may not involve real people, and it contains sample recommendations on masks and links to some CDC publications, including research abstracts citing “Science Advances” articles.                                              Anhui Center one of white list in Europe , KF94 ,KN95,Flat face mask all can production ,also can offer customized package and design , any questions and inquiry freely ask info@medical-best.com .                                            


Post time: Nov-12-2021