Recently, Denmark announced the results of a clinical trial of "wearing a mask to prevent covid-19" [1]. This clinical trial recruited about 6000 people who need to be outdoors for at least 3 hours a day. They were randomly divided into two groups. One group was a control group and only required to maintain social distance during outdoor activities. The other group was a mask group, except for keeping social Distance, it is also required to wear a mask. Participants in the mask group also received 50 Face Masks.

  ffp2 mask

The test lasted for a month, and a total of 4862 people completed the test. Statistics found that 53 people in the control group were infected, with an infection rate of 2.1%; 42 people in the Mask group were infected, with an infection rate of 1.8%.


From the results, the proportion of infection in the mask group has been reduced by 0.3%, and the risk of infection has been reduced by 15%. However, because this range is too small, the reduction effect is not obvious.


Therefore, when someone sees this result, they will say that wearing a mask may be useful, but it is not very useful!


Is that true? If you look closely at the data of this clinical trial, you can find a "reversal": because of the problem of the evaluation criteria, the effect of the mask is underestimated!


In this test, whether there is a virus infection, it only needs to meet any one of the following conditions:

  1. Anti-covid-19 antibody positive;
  2. Nucleic acid positive;
  3. The hospital diagnosed covid-19 pneumonia based on symptoms


A total of 95 "infected persons" appeared in this test, 90% of which were diagnosed because of antibody positive, which hides a huge problem: because antibody positive is not a recognized standard for the diagnosis of infection.


Antibody tests are prone to false positives. Many people who are not infected will also have positive results for antibody tests. Among these 4862 people, the proportion of antibody positive is 1.3% to 1.5%, which is also the false positive range of general antibody testing.


If the test adopts the standards of vaccine clinical trials and is subject to nucleic acid testing, what will be the result?


According to the nucleic acid test results, 5 people in the control group were infected, and the infection rate was 0.2%; there was no infection in the mask group, and the infection rate was 0%. The protection rate of the Mask reaches 100%!


Some people only have clinical symptoms of covid-19 pneumonia, but no nucleic acid test results. Even if these numbers are taken into account, using nucleic acid positive and clinical symptoms as diagnostic criteria, the protection rate of masks is 66%!


Compared with the previous covid-19 vaccine developed by Oxford University, if the full dose is injected twice, the protection rate is only 62%!


Of course, the protection rate of masks cannot be reliably concluded from the current clinical practice, but it can be said with certainty that it will not only be 15%, it is very likely to be higher than 66%!


Please note that it is not to say that masks can replace vaccines, because there will always be times when masks are removed, but it should be normal to wear Masks before the global disappearance of the virus.