CDC experts on masks:

Community mask wearing substantially reduces transmission of #SARSCoV2 in 2 ways:

📍Source control of exhalation

📍Protecting the wearer

➡️ But they are *not equal*. CDC just advised double masking.

Important explainer 🧵.
jamanetwork.com/journals/jama/…
2) First, masks prevent infected persons from exposing others by blocking exhalation of virus-containing droplets into the air (termed source control)—important because at least 50% or more of transmissions are from presymptomatic & asymptomatic #COVID19 cases.
3) In recent laboratory experiments, multilayer cloth masks were more effective than single-layer masks, blocking as much as 50% to 70% of exhaled small droplets and particles.2,3 In some cases, cloth masks have performed similar to surgical or procedure masks for source control.
4) Second, masks protect uninfected wearers. Masks form a barrier to large respiratory droplets that could land on exposed mucous membranes of the eye, nose, and mouth. Masks can also partially filter out small droplets and particles from inhaled air.
5) Multiple layers of fabric & higher thread counts improve filtration. However, **effectiveness of cloth masks to protect the wearer is lower than their effectiveness for source control**, and filtration capacity of cloth masks can be highly dependent on design, fit, & materials
6) CDC just released new recommendations to either double mask with at least cloth + surgical, or tighten the fit of surgical masks with special technique.
7) In the new CDC study, having both the source and receiver masks is best. But if only one is masked, then double masks seems better (comparing purple circles below).
8) Also notice that if only one sloppily fitted surgical mask is worn by one person, it’s more critical that the SOURCE person exhaling the virus wears it. (Red circles)
9) Also, there is a glaring finding that one sloppy mask worn by the receiver actually doesn’t give enough protection much at all (yellow circle). But if double masked or carefully fitted & sealed, receiver only masking does work!!!
10) This is why we need to tell people that a sloppy mask is very poor protection. If only one mask, then use a medical grade surgical one—and make sure it is tied this way...
11) “Epidemiology has helped quantify the benefit of mask wearing. At a hair salon in which all staff and clients were required to wear a mask under local ordinance, 2 symptomatic, infected stylists attended to 139 clients and no infections were observed in the 67 clients”
12) During a COVID-19 outbreak on the USS Theodore Roosevelt, persons who wore masks experienced a 70% lower risk of testing positive for SARS-CoV-2 infection. Similar reductions found when contacts were masked5 and in household clusters in which household members were masked.6
14) “increasing number of studies have also provided persuasive evidence that universal mandatory mask wearing policies have been associated with reductions in the number or rate of infections and deaths (Table).
15) “These studies did not distinguish the types of masks used in the community. The association is strengthened because, in many cases, other mitigation strategies had already been deployed before enactment of mask wearing policies, after which reductions were (still!) observed.
16) “A study that examined changes in growth of infections in 15 states & DC before and after mask mandates showed that growth before the mandates were enacted, but slowed significantly after, with greater benefit the longer the mandates had been in place. pubmed.ncbi.nlm.nih.gov/32543923/
17) “children aged 7 to 13 years have been shown to be able to make accurate inferences about the emotions of others with partially covered faces, and FDA recently approved a transparent surgical mask that may be useful in such circumstances. pubmed.ncbi.nlm.nih.gov/33362251/
18) Concerns about reduced oxygen saturation and carbon dioxide retention when wearing a mask have not been supported by available data. pubmed.ncbi.nlm.nih.gov/33003954/
19) “Similar to principle of herd immunity for vaccination, the greater the extent to which mask wearing in this case—is adopted by the community, the larger the benefit to each individual. (Greater) mask use in community may be of greater importance than the type of mask worn”
20) “It merits noting that a recent study has been improperly characterized as showing that cloth or surgical masks offer no benefit. This randomized trial in 🇩🇰 was (**only**) designed to detect >50% reduction in risk for persons wearing surgical masks.
21) “...Findings were inconclusive, most likely because the actual reduction in exposure these masks provided for the wearer was lower.
22) “More importantly, the study was far too small (ie, enrolled about 0.1% of the population) to assess the community benefit achieved when wearer protection is combined with reduced source transmission from mask wearers to others”.
23) Basically, that Danish study was not informative or useful for interpretation, as deemed by the CDC authors. jamanetwork.com/journals/jama/…
24) I want to reemphasize this figure from the recent CDC study (see links in posts above)— everyone masking clearly more effective than 1 person masking. And if only 1 person, double masking better than poor unfitted surgical mask.
25) The other thing to consider is, where available, if possible, switch to premium masks from just cloth. Assuming tight fit, premium offers better filtration than cloth or surgical masks alone. The new #B117 is just too infectious. Take more precautions.

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More from @DrEricDing

13 Feb
We need to call Moderna vaccine by the true proper name of “NIH-Moderna vaccine”. It was mainly developed at Fauci’s NIAID. Moderna honed its mRNA tech via DARPA grants & also didn’t disclose federal support in patents, violating Bayh-Dole Act. HT @mattbc.
2) @mattbc is right in calling out this nonsense by Moderna to hide it got tremendous federal support for the vaccine in its patent. This is a violation of the 1980 Bayh-Dole Act. And @moderna_tx possibly violated it by not disclosing in 154 patent apps.
washingtonpost.com/business/2020/…
3) Moderna vaccine works folks. @KizzyPhD from the NIH is famously one of the co inventors of the vaccine. But this doesn’t change that Moderna needs to publicly acknowledge in its patents that its vaccine was taxpayer funded and NIH co developed, akin to Oxford-AstraZeneca.
Read 4 tweets
12 Feb
What is missing from this CDC school reopening priority list? Airborne virus guidance! Like almost nothing in 33 page document on ventilation except 1 paragraph on open the windows, but only if feasible. Ventilation should be #2 behind masks! #COVID19
cdc.gov/coronavirus/20… Image
2) Notably absent from new CDC guidance was ventilation. In one short paragraph, CDC suggested schools open windows & doors to increase circulation, but said they should not be “if doing so poses a safety risk or a health risk.” #COVID19 nytimes.com/2021/02/12/hea…
3) “C.D.C. gives lip service to ventilation in its report, and you have to search to find it,” said @j_g_allen, an expert on building safety at the Harvard T.H. Chan School of Public Health in Boston. “It’s not as prominent as it should be.”
Read 10 tweets
12 Feb
Worrisome—UK 🇬🇧 data shows suddenly higher #COVID19 positivity % in England 🏴󠁧󠁢󠁥󠁮󠁧󠁿 (where #B117 highly dominant) in children ages 5-9, in both boys and girls, sustained each week over 4 consecutive weeks. Ages 0-4 positivity also increasing. Israel 🇮🇱 has also seen kids case trend. Image
2) As noted by @dgurdasani1, this is all despite these data really underestimating infection in children (as they are based on symptom based testing). And positivity rates appear highest in early year settings (fully open) & primary schools (20% attendance).
3) Dr @dgurdasani1 believe it is related to schools in England 🏴󠁧󠁢󠁥󠁮󠁧󠁿.
Read 13 tweets
12 Feb
⚠️REINFECTION WARNING from the WHO.

“We are now getting reports of people getting reinfected with a new variant—from 🇿🇦 (#B1351)—suggesting people who’ve had prior infection could get infected again.” says Chief Scientist Dr. Soumya Swaminathan. #COVID19
2) This comes on the heels of troubling data I highlighted last week from the placebo group of the Novavax 🇿🇦 trial that that people previously infected and have #COVID19 antibodies (seropositive) has no protection for #B1351 variant reinfection— not even for severe disease!
3) Last month, South Africa’s CDC also warned about likelihood of reinfection risk because of the lower virus neutralization seen by the E484K mutation in the #B1351 variant.
Read 13 tweets
12 Feb
Vaccinations have gone from 900k per day to now over 1.5 million.

I think Biden’s team under @aslavitt46 & @JeffZients @WHCOVIDResponse can push it to 2 million by the end of Feb / early March, and hopefully 3 million a day by mid April.

Let’s do it. #COVID19 (HT @CAPAction) Image
3) These PSA campaigns with @Adweek and @WarnerMedia and @GalGadot are also effective.
Read 4 tweets
12 Feb
Moderna says it has 631.5 mil doses of #COVID19 vaccines on order, of which a whopping 613 million are committed to rich countries like 🇺🇸 🇪🇺 🇯🇵 🇨🇦 🇰🇷🇨🇭🇬🇧 🇮🇱—almost none to developing countries. For COVAX, Moderna vaccine not listed among providers. Sad.
investors.modernatx.com/news-releases/… Image
2) Moderna says it has more countries not disclosed. Why? Poor countries likely wouldn’t hide it. The complete absence of Moderna from discounted COVAX vaccine providers shows where its values for humanity are. @moderna_tx — show you care. Donate to COVAX. gavi.org/sites/default/…
3) While most of COVAX vaccines to developing countries are Oxford AstraZeneca vaccines, Pfizer is also among them, even though it has ultra cold chain requirements. Moderna doesn’t need ultra cold storage. So @moderna_tx has no excuse. gavi.org/sites/default/… Image
Read 4 tweets

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