You could compare different types of masks that were manufactured to have the same appearance.
Not really. If I told you that 93% of Americans predominantly wore masks as recommended, 46% of that exactly as recommended, would you be disappointed?
What does “47% predominantly as recommended” even mean when the participants are self reporting? Where does it say someone followed along with participants?
Also, were participants testing themselves?
Finally, I do see a difference in Table 2 for PCR test and healthcare diagnosis. What could be wrong with the
Here’s the problems with this study:
- Wasn’t Denmark in lockdown or partial lockdown in April-May? So the positives being dealt with are small as are exposures.
- If participants tested themselves, this is a major issue.
- Not everyone wore masks properly with waffle terms of “predominantly”. What does that mean?
- Statistical analysis was set for a 50% reduction. Why? Table 2 does show a difference to me for PCR test and diagnosis (double for not wearing mask).
- Reliance on antibodies for their differences is problematic since the appearance of antibodies can be delayed for weeks. Someone could have been exposed prior to the study.
- Surgical masks are not designed to protect the wearer because they have gaps. There are better masks available to the public that addresses this problem. You can also fix the gaps of the surgical mask.
Taken together, it’s no surprise that the results are inconclusive.
Why are we discussing this paper anyway? It’s flawed and relatively old. There’s plenty of new data out there.
If you told me that 93% of Americans self-reported that they predominantly wore masks as recommended, and 46% of that, exactly as recommended, yes, I would be disappointed. I’m pretty certain the numbers in my neck of the woods are higher than that, fwiw.
Well, that’s your guess. Mine is that 93% is about as high as you’re going to get in the real world. I doubt seatbelt use is much higher.
Only it’s not 93%, it’s 46%. Plus people who reply “yeah, mostly” on a survey. And I see more compliance than that walking around my neighborhood.
Come on. It’s not “yeah, mostly” on a survey. It’s people who’ve chosen to participate in a scientific experiment. Gotta say, don’t see as much effort to pooh pooh any of the studies showing mask usefulness.
Here’s an article in the NYT about the research finding. https://www.nytimes.com/2020/11/18/health/coronavirus-masks-denmark.html
Critics were quick to note the study’s limitations, among them that the design depended heavily on participants reporting their own test results and behavior, at a time when both mask-wearing and infection were rare in Denmark.
The incidence of infections in Denmark was lower than it is today in many places, meaning the effectiveness of masks for wearers may have been harder to detect
protection conferred by masks on the wearer trended “in the direction of benefit” in the trial, even if the results were not statistically significant.
I’ll make one more note on the testing and diagnosis. Only 15 of those 5000 participants were diagnosed with covid-19 by healthcare professionals with 5 wearing masks and 10 not wearing masks. Another 5 people who didn’t wear masks had positive self-reported PCR tests while none of the people who wore masks had positive PCR tests. That’s only a 0.4% infection rate.
The authors relied mostly on antibody testing performed by the participants to make their conclusions. Meanwhile, daily cases in Denmark had dropped in half from about 160 to 80 cases. I checked, they were just starting to reopen and didn’t open restaurants and bars until the end of May. So many of those positive antibody tests could have been due to exposures prior to the study where the titers were not high enough to detect for the baseline. In addition, there is speculation (with limited evidence) that masks and physical distancing reduce the viral inoculum.
But again, masks are more for source control unless you buy good ones that are layered and have a good seal and/or you also wear a shield.
For what it’s worth, here’s an oft-cited paper that was withdrawn:
Withdrawal The authors have withdrawn this manuscript because there are increased rates of SARS- CoV-2 cases in the areas that we originally analyzed in this study. New analyses in the context of the third surge in the United States are therefore needed and will be undertaken directly in conjunction with the creators of the publicly-available databases on cases, hospitalizations, testing rates. Etc. We will be performing this in conjunction with machine learning experts at UCSF. Therefore, the authors do not wish this work to be cited as reference for the project. We hope to have an updated analysis using data from the 2nd and now 3rd wave of SARS-CoV-2 in this country soon. If you have any questions, please contact the corresponding author.
It’s really, really hard to squeeze rigorous science out of these observational studies during this pandemic because of how hard it is to get around the confounders.
It is perhaps not unlikely that masks could have a mildly beneficial effect that is, for all intents and purposes, made negligible by those confounders.
If #2 above is actually true, then then the notion that all would be well if we could just (somehow) get to 95% compliance is called into question.
While I appreciate your take on things and admire the way in which you convey it, I would counter this by asking how the observational data related to present outbreaks supports the theory or is at all overwhelming. Are there far more unmasked places experiencing spread right now than masked places? My reading says the opposite is true – and in a very, very overwhelming way.