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16 Oct, 4 tweets, 2 min read
NEW: There's an emerging argument that masks don't actually work. It's based on a recent study published by the CDC, which reportedly showed that 85% of mask-wearers contract #COVID19. This is a dangerous mischaracterization of the study. Here's what the work really showed:
CDC looked at 154 adults with symptomatic #COVID19 and compared them to an uninfected control group. Of the patients with #coronavirus, 70.6% reported ALWAYS wearing a mask and 14.4% OFTEN did. From a distance, it looks like 85% of mask-wearers got COVID.
cdc.gov/mmwr/volumes/6…
But you've got to read the actual study. Here's the key detail: COVID patients were twice as likely to have dined at a restaurant. Why does this matter? Because people take off masks to eat. You might report that you ALWAYS wear a mask but we know it comes off when you're eating.
The takeaway from this study: Restaurants appear to be an important risk factor for #coronavirus transmission. As we reopen society, researchers are trying to find ways to make dining more safe, but they are not questioning the use of masks. You shouldn't either.

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More from @DrMattMcCarthy

Matt McCarthy Profile picture
17 Oct
UPDATE: The #coronavirus case fatality rate continues to drop. Here's one reason that doesn't get a lot of attention: We're getting much better at triage. During the first few months, we really couldn't tell which hospitalized patients were going to get worse. That has changed:
Why were we bad at this? Many with #COVD19 suffer from 'silent hypoxemia,' where oxygen levels appear incompatible with life yet patients feel no symptoms. The President may have had a subtle, less aggressive variation of this when he was airlifted to Walter Reed but felt fine.
Vital signs have proven unreliable for effective triage, so we've turned to lab tests for help. One that quickly emerged as a potentially-helpful candidate was interleukin-6 (IL-6), a marker of inflammation that is usually absent (or present in low levels) in blood.
Read 8 tweets
Matt McCarthy Profile picture
16 Oct
This is a stunning and inaccurate claim. Rewriting history is a mistake. Some key points about the #coronavirus surge in New York City:
1. Our stockpiles of PPE were unable to withstand the first wave. We went from using 4k masks/day to 40k masks/day to 90,000 masks/day at the peak & we did not have the stockpiles to keep up.
2. Hospitals had to create I.C.U.s out of operating rooms, procedure suites, and conference areas. We created ventilators out of anesthesia machines and split ventilators to help two patients simultaneously. We redeployed doctors to the ICU who didn't typically work there.
Read 5 tweets
Matt McCarthy Profile picture
14 Oct
1. Employees should stay home for 14 days after contact (within 6 feet for 15 minutes) with a person who has #COVID19. Period. Even if someone tests negative or feels well, they must quarantine for the full 2 weeks because symptoms can appear 2 to 14 days after exposure.
2. Mike Pence's VP debate appearance 11 days after the ceremony led many to believe that quarantine can terminate early with a negative test. This fallacy was reinforced by the CDC Director, who cited "serial negative test results" to end quarantine early. That is not a thing.
3. It's possible, although unlikely, to develop symptoms more than 14 days after exposure. The Labor Secretary's wife, Trish Scalia, attended the Rose Garden ceremony and tested positive outside of this window. It is unclear when her infection occurred.
Read 4 tweets
Matt McCarthy Profile picture
13 Oct
UPDATE: I expect a recommendation for the general public to continue wearing masks EVEN AFTER a #coronavirus vaccine is rolled out. This is rarely mentioned in discussions of Operation Warp Speed, but the first #COVID19 vaccines may offer only moderate protection. Some thoughts:
1. Approval of a #COVID19 vaccine does not mean a quick return to normal. Volunteers who receive a "successful" vaccine may still get sick. (In June, the FDA set target efficacy at 50%). There will be protection, but it could be leaky. We haven't prepared the public for that.
2. Johnson & Johnson and AstraZeneca have paused trials to explore illnesses in volunteers. We should be reassured by this transparency, not alarmed. Adverse events are an expected part of any large study. Potentially noteworthy that both use adenovirus vectors to deliver genes.
Read 4 tweets
Matt McCarthy Profile picture
10 Oct
UPDATE: The President is set to resume in-person events today. Here's how I think about the potential danger he poses to others:
I want to know if he still has "replication-competent virus" in his system. (I don't actually care if he tests positive today on some rapid test). We're confident that for mild & moderate COVID19, patients no longer have replication-competent virus 10 days after onset of symptoms
But if he had severe #COVID19 (hypoxia, >50% lung involvement on imaging), he could be contagious for longer than 10 days. Based on what we know, he appears to have had moderate COVID19. (I seem to be in the minority in this assessment).
Read 4 tweets
Matt McCarthy Profile picture
8 Oct
Often asked for my opinion of the latest #COVD19 therapeutic. Yesterday it was the antibody cocktail. Here's how I think about this stuff:
For any new treatment, I want to know if it's 1) safe and 2) effective. I also look at distribution mechanisms. Do we have a way to get this thing to the people who need it? In many cases, the answer is no.
I'm not bullish on antibody cocktails because there's a mismatch between supply & demand. Urgent care clinics don't want to administer cocktails because the infusion is time-consuming and reimbursements are low. Primary care clinics will feel a similar crunch. So what happens?
Read 4 tweets

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