“𝐖𝐚𝐢𝐭, 𝐝𝐢𝐝 𝐭𝐡𝐞 𝐌𝐌𝐖𝐑 𝐫𝐞𝐚𝐥𝐥𝐲 𝐬𝐚𝐲 𝐦𝐚𝐬𝐤𝐬 𝐝𝐨𝐧’𝐭 𝐰𝐨𝐫𝐤?”

Ugh. If you haven’t seen it circulating on FB, you probably will today. Or someone will send you the meme/only table 2.

The recent MMWR (I still think it’s awesome people kindof know what that is now…us-nerdy-people have been reading it for years like it’s our favorite novel) talked about a small study comparing people with and without confirmed COVID-19.

Then people did a quick cut-and-paste with Table 2 – and, claimed “See! Masks don’t work”.

Wait, what? Whoa. Lemme’ help…

1. The study was among 314 people. Y’all 3.1.4 people. Is that representative of the US? Nope. In epidemiology terms, we call that not-generalizable.

2. The study was a case-control study. We often use this type of study design in epidemiology and this one was designed well. When we do these studies, we understand the advantages and biases. Some major biases for this design include recall bias (so, asking someone to remember what they did weeks ago in a yes/no format and hoping they remember correctly) and selection bias (so, the participants likely look different than the general population).

B𝐮𝐭, 𝐭𝐡𝐞 𝐫𝐞𝐚𝐥 𝐢𝐬𝐬𝐮𝐞 𝐢𝐬 #𝟑 𝐛𝐞𝐥𝐨𝐰…

3. The real conclusion of the study showed where someone was at risk of getting COVID-19 among the 314 people. Where was that? At a restaurant/bar and home with an infected family member – ALL of these experiences are more likely to include no masks anyways (you take it off to eat and generally people don’t wear it in their own home). So, of course they don’t work in those settings – because people usually aren’t wearing them.

The study is not about masking or not masking. It’s about where this group of 314 likely contracted COVID-19. In settings probably without masks. So, after all of that – the study points to the strength of masking, not the negation of it.

C𝐨𝐧𝐭𝐞𝐱𝐭 𝐦𝐚𝐭𝐭𝐞𝐫𝐬. 𝐒𝐭𝐮𝐝𝐲 𝐝𝐞𝐬𝐢𝐠𝐧𝐬 𝐦𝐚𝐭𝐭𝐞𝐫. 𝐏𝐚𝐫𝐭𝐢𝐜𝐢𝐩𝐚𝐧𝐭𝐬 𝐰𝐡𝐨 𝐝𝐨 𝐨𝐫 𝐝𝐨 𝐧𝐨𝐭 𝐚𝐠𝐫𝐞𝐞 𝐭𝐨 𝐛𝐞 𝐢𝐧 𝐭𝐡𝐞 𝐬𝐭𝐮𝐝𝐲 𝐦𝐚𝐭𝐭𝐞𝐫. (𝐁𝐓𝐖, 𝐭𝐡𝐞 𝐌𝐌𝐖𝐑 𝐚𝐥𝐬𝐨 𝐭𝐚𝐥𝐤𝐬 𝐚𝐛𝐨𝐮𝐭 𝐭𝐡𝐞𝐬𝐞 𝐥𝐢𝐦𝐢𝐭𝐚𝐭𝐢𝐨𝐧𝐬 𝐢𝐧 𝐭𝐡𝐞 𝐟𝐮𝐥𝐥 𝐰𝐫𝐢𝐭𝐞-𝐮𝐩 𝐢𝐟 𝐲𝐨𝐮 𝐫𝐞𝐚𝐝 𝐢𝐭.)

𝐓𝐰𝐨 𝐭𝐡𝐢𝐧𝐠𝐬 𝐰𝐡𝐞𝐧 𝐲𝐨𝐮’𝐫𝐞 𝐫𝐞𝐚𝐝𝐢𝐧𝐠 𝐚 𝐬𝐜𝐢𝐞𝐧𝐭𝐢𝐟𝐢𝐜 𝐚𝐫𝐭𝐢𝐜𝐥𝐞:

1. Does it agree or disagree with the preponderance of evidence that came before it? That’s science, isn’t it! We test and re-test and re-test some more and then re-test – it builds a mountain of scientific evidence that stands with rigor. In this case, one study of 314 does not negate the 1000s of data points, studies, and evidence we have on the effectiveness of masks. (I linked to some of those at the end).

2. Don’t be a velociraptor and share everything too quickly. Many of you don’t and I heard you today! =) Interpreting the science matters with these viral things (remember how fake news spreads 6 times more than real news – from the ‘Social Dilemma’).

3. If a study comes out showing masks are harmful or don’t work, I will be the first to tell you. =) Until then, wear your masks. If you want to look at the mountain of evidence we do have, look at the few posts I put below.

-Friendly neighbor epidemiologist


Read the WHOLE MMWR study (starts on page 26) including the discussion section. https://www.cdc.gov/mmwr/volumes/69/wr/pdfs/mm6936-H.pdf?deliveryName=DM37614&fbclid=IwAR0hh6WT3C9i-7DDWGZVWnvNfMKyvrfleM9l-uDguc4ExUwB5PiICZevjyM


1. Masks work: The strongest evidence we have https://tinyurl.com/yxkymuof https://tinyurl.com/y2ux4owk

2. Mask 101: Why they work, exposure time, how to wear and disinfect your mask correctly https://tinyurl.com/yxvayp76 https://tinyurl.com/y6zxl2u3

3. Myth-busters for mask: A LONG post debunking common myths about masks (masks work realy well, clearing up what the surgeon general/WHO said, CO2 fears) https://tinyurl.com/y642sefb

4. Did the Surgeon General or WHO say not to wear masks? https://tinyurl.com/y4d8ghk2

5. Sheltering in place works https://tinyurl.com/y66halh3 https://tinyurl.com/y2cn5vdq

6. Let’s talk masks, face shields, and gaiters: Why you need to pull your masks over your nose – https://tinyurl.com/y5rfqhqk

7. Why state-wide mask mandates work! – https://tinyurl.com/yxu6gl4r

8. A reminder of when someone is contagious and the importance of masks (and a note on bipartisan science) – https://tinyurl.com/y4rfjmc5

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