156. Mask, COVID-19, Annals of Internal Medicine

Questioning medicine daily


https://www.acpjournals.org/doi/10.7326/M20-7448

https://www.acpjournals.org/doi/10.7326/M20-6817

Effectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers
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A Randomized Controlled Trial

Masks!!!! Do they prevent COVID19 transmission by preventing spread from infected people to others OR do they work by protecting wearers OR is it both.
We now have an answer to the second question, Do the mask work by protecting the wearers and in short the answer is no.
Fresh out november 18.
The DANMASK-19 trial

It a trial designed to examine the masks' protective effect.

Spring 2020 in Denmark, Social distancing recommendations were in effect, but masks were not recommended, they were rarely worn outside of hospitals, and the infection rate was modest around 2% per month which is pretty close to what we were seeing because remember we were around 1-3% here in american depending on where you lived with some places much much higher like New york but many places down to almost 0% like the fly over states and even places like salt lake city.
The endpoint was infection in the mask wearer!!! NOT infection in their contacts or the overall community infection rate.

This study enrolled 6024 adults who spent at least 3 hours outside their homes per day, had occupations that did not require masks, and did not have a previous known diagnosis of SARS-CoV-2 infection.
All participants were told to follow social distancing measures but randomized to wear or not wear a mask when outside the home.

The primary outcome was SARS-CoV-2 infection, defined as a positive COVID nasal swab OR development of a positive COVID antibody test OR a hospital-based diagnosis of COVID-19.
They powered it to find a 50% reduction in infection risk
After 1 month of follow-up, 1.8% (42 of 2392) of participants in the mask group and 2.1% (53 of 2470) in the control group developed COVID19 infection (risk difference, −0.3 percentage point [95% CI, −1.2 to 0.4 percentage point] [P = 0.38]; odds ratio, 0.82 [CI, 0.54 to 1.23] [P = 0.33]).
THERE WAS NO DIFFERENCE!!

BOOM FIRST RCT we have on wearing mask during COVID19 pandemic and it says that wearing a mask does not protect you from getting COVID19.
As with all trials which dont show what you want them to show there are people already knocking this well done trial. This is a common event and happens often in the cardiology or vit d literature. The study doesnt show what they want to they use very simplistic thinking to knock it down. Don’t get me wrong it has it’s flaws but use your brain to think deep and dont use the easy answer because they are not correct, in my opinion
Here are some of the things I have heard people say
1- “Well the study only looked at the effect of recommending mask use, not the effect of actually wearing them.”-In the study people were recommended to wear a mask not required to wear one-- yes, but that goes for every study—we recommend you to take a pill not the effect of actually taking them since we have no way of knowing they actually took them…This is every trial and either you believe in science and trials or you dont and you cant now all of a sudden not believe in medicine because the trial didnt show what you wanted.
2- How do we know people are wearing mask accurately??? Well in the trial 46% wore the mask as recommended and 47% wore it "predominantly as recommended," for a total of 93%. That is probably better than america, go to the grocery store and just walk around you might need more noses than heads of lettuce.
3- Some people say well this was done in denmark, we live in america so you cant use this evidence in america. This arguement works for some conditions and some treatments but I have no idea how this arguements works for wearing and not wearing mask. Unless there is a cultural difference in Denmark I am not aware of.
AND FINALLY---
4- Some say it is irresponsible to publish these results because this will give antimask people ammo--- I couldn't disagree any more-- More irresponsible would be to not publish the results of carefully designed research because the findings were not as favorable or definitive as some may have hoped. Science is not to be cherry picked






Here are one of the issues that are deeper thinking
Remember-
1) They powered it to find a 50% reduction in infection risk-- remember when you power your study you power it to find an outcome that you think is worth finding. Sure maybe they could find maybe a 1% reduction and it would be a positive study but people would say wait these stupid mask only give me a 1% reduction?? Also the smaller the benefit you want to find the more people you have to enroll. If you only wanted to find a true 1% difference you have to enroll over a million people depending on your standard deviation. That is just not feasible.
2) either you believe in science or you dont and if you want randomized control trials for the medications that you prescribe then you need have to be ok with them for mask that you tell your patient to wear. You dont get to change your belief on RCT because it didnt show what you wanted.
And finally
3) This trial does not tell us that mask dont work. We dont know if mask work to prevent us from spreading covid19 to other individuals. That trial could be done and should be done. You would have to randomized cities or areas to mask and no mask and see what happens. It would have to be done in other countries or small town america
My final thoughts are
Lots of people want to knock this study because it didnt show what they wanted- People wanted this to show how great mask are. People want to believe mask are a holy grail of wonderfulness. They want to shame people and post memes on social media shaming those individuals for not wearing a mask. in the end this study is a well done study that gives us good information. Unfortunately mask have become such a strong belief. It is like antivaccine people, their belief of evidence is much stronger than the actual evidence. Mask have sadly become political not science. I am not saying dont wear a mask and Im not saying always wear a mask. Do your best to try to wear them but if you dont have one on or you forget one, its OK!!! Mask are not parachutes. They are far from it. With all things being equal the NNT of masks is likely in the millions, especially for events we care about. Remember we don't care about catching a virus, people catch viruses all the time!! EVERY SINGLE DAY! Keep in mind we care if you have any morbidity and mortality from the virus. The event rate is still just a fraction of a fraction of a percent.

And with that!

Thanks for listening, thanks for your time and until next time keep the quest in questioning medicine