CDC ... I might even go as far as to say,

[therealnickb]

[elSquid]

Seems legit.

I guess if you want to be absolutely literal, then yes a mask will protect a person more than a vaccine that doesn't work in that particular individual.



The message that the CDC is apparently fine with: skip the vaccine, just wear a mask instead. 'Cause that'll work well, right?

-- Michael

[as_rocketman]

He's not wrong but there's a lot of assumptions going into it.

Conscientious facemasking is probably > 99% effective. But you have to do it properly and you have to do it whenever there's a threat, potentially forever. Many people don't or can't use them well. Anyone with small children knows exactly what I mean.

Vaccines will not be 100%, but then they aren't supposed to be -- for many people they will mitigate symptoms but not totally eliminate them. However CDC has a target of > 80% effectiveness before they'll authorize release, if I remember the last round of discussion correctly. In practice protection levels of > 95% are often achieved, but not 100%.

However, vaccination is a one-and-done (or two-and-done, probably) action, and it takes other carriers off the table faster than natural progression, thereby reducing the number of critical contacts.

TLDR; apples and oranges. CDC flack wants you to do both and is trying to be simple and cute in his language.

[elSquid]

Conscientious facemasking is probably > 99% effective.

What leads you to that conclusion, or is this just an exaggeration for effect?

-- Michael

[balgor]

What leads you to that conclusion, or is this just an exaggeration for effect?

-- Michael

The key part of Rocketman's statement is "used properly". Properly fitted and used in the proper environment. Even medical personnel who are well trained and constantly reminded about proper use make mistakes with PPE.

A mask + faceshield appears to be relatively bullet proof at stopping Covid infections.

https://jamanetwork.com/journals/jama/fullarticle/2769693

It's an Indian study of health care workers visiting hundreds of potentially infected people.

If, everyone wore masks 100% of the time in any environment in which transmission is possible, then the R0 would be reduced. You get R0<1 and transmission will eventually stop.

[as_rocketman]

What leads you to that conclusion, or is this just an exaggeration for effect?

-- Michael

Here is a decent first-principles model for the mechanics of transmission.

We know the size and rate of shedding of droplets required for reliable person-to-person transmission. Those droplets are unchallenging to basic PPE, unless you are in extended contact or there's some other extenuating circumstance, or you're deliberately testing the boundaries of what constitutes a proper facemask.

There will shortly be a brigade of cranks citing oblique studies showing they don't work (they are wrong) or saying most people don't even need them with a little sunlight and distance (they are at least partially right), but the mechanics are actually pretty simple and well understood. Having said that, few people do in fact use them properly, and over a long period of time the occasional failure is inevitable.

[elSquid]

A mask + faceshield appears to be relatively bullet proof at stopping Covid infections.

https://jamanetwork.com/journals/jama/fullarticle/2769693

It's an Indian study of health care workers visiting hundreds of potentially infected people.

Before face shields, 62 workers (40 women) visited 5880 homes with 31 164 persons. From the 5880 homes visited, 222 persons tested positive for SARS-CoV-2, between May 4 to May 13. Twelve workers (19%) were infected during this period. Eight developed symptoms (fever, cough, sore throat, myalgia, and anosmia) and 4 were asymptomatic. The 12 infected workers were moved to care centers. Four developed desaturation and mild breathing difficulty and were treated with oral hydroxychloroquine and oxygen therapy; all 4 recovered. Contact tracing of the workers who tested positive identified 14 van drivers, who were monitored. All were asymptomatic and tested negative between day 7 and 10 after contact with the workers.

After face shields, 50 workers (previously uninfected) continued to provide counseling, visiting 18 228 homes. Among the counseled, 118 428 persons, 2682 subsequently tested positive for SARS-CoV-2. No worker developed asymptomatic or symptomatic infection.

That study seemed to show that masks weren't "99% effective", since it was the face shields that cut the infections to zero.

I'd be curious to see what would happen in a ( no mask but faceshield ) group.

OTOH, I guess that this is another HQC success story!

-- Michael

[elSquid]

Here is a decent first-principles model for the mechanics of transmission.

We know the size and rate of shedding of droplets required for reliable person-to-person transmission. Those droplets are unchallenging to basic PPE, unless you are in extended contact or there's some other extenuating circumstance, or you're deliberately testing the boundaries of what constitutes a proper facemask.

No doubt masks stop droplets on the source side in a meaningful way, however has aerosolization been completely ruled out?

-- Michael

[as_rocketman]

Yup. Not enough virions can be carried in an aerosol. This isn't measles. I mean, you can't rule it out completely, but it would take some extraordinary circumstances for this to be feasible.

A paper I referenced in another thread recently demonstrated, through phylogenetic analysis, that under most conditions the replication rate is actually pretty low, only that there are "super-spreader" events that create an aggregate of high transmissibility. These events are rare to the point that they are detectable as genetic bottlenecks. You wouldn't see this if aerosol transmission was favored.

[therealnickb]

But, for 3 months plus we’ve been hearing...

“Masks don’t protect you. They protect everyone else.”

Now suddenly, masks protect you! And even better than a vaccine. WTF?

[jbj]

CDC ... I might even go as far as to say,

No doubt masks stop droplets on the source side in a meaningful way, however has aerosolization been completely ruled out?

-- Michael

It has not been ruled out. And the two outbreaks that point towards that, the church choir incident early in these events, and St. Michael Medical Center last month (both in Washington state), along with asymptomatic spread (mostly inferred at this point, AFAIK) certainly are concerning. But rare as as_rocketman states above.

But in all of the above, it is the prolonged exposure that stands out.


Sent from my iPhone using Tapatalk

[duenor]

But, for 3 months plus we’ve been hearing...

“Masks don’t protect you. They protect everyone else.”

Now suddenly, masks protect you! And even better than a vaccine. WTF?

Government leaders wrongly assumed that people who would be unwilling to wear a mask for their own safety, would do it out of consideration for others. This kind of messaging became misconstrued to mean that masks are somehow unable to protect the wearer, but can protect others. This misconception doesn't make sense, or hold up to any kind of fact finding scrutiny, but some people have seized onto it as evidence that masks don't work. The same is true of the misconception regarding Redfield's commentary about masks and vaccines, although to be fair Redfield's words were poorly chosen at best.

[duenor]

Yup. Not enough virions can be carried in an aerosol. This isn't measles. I mean, you can't rule it out completely, but it would take some extraordinary circumstances for this to be feasible.

A paper I referenced in another thread recently demonstrated, through phylogenetic analysis, that under most conditions the replication rate is actually pretty low, only that there are "super-spreader" events that create an aggregate of high transmissibility. These events are rare to the point that they are detectable as genetic bottlenecks. You wouldn't see this if aerosol transmission was favored.

Does that mean that the normal R0 is fairly low, except at rare events where it goes extremely high and then as a result boosts the overall R0?

[DentonandSasquatchShow]

Wash your freakin' hands you disgusting pigs.

End of story!

[as_rocketman]

Does that mean that the normal R0 is fairly low, except at rare events where it goes extremely high and then as a result boosts the overall R0?

That's my interpretation of the data and the latest papers. I haven't yet found a paper that lays out this hypothesis directly.

Reproduction number Rt is a complex function of hidden variables. We tend to think in terms of R0, the basic reproduction number, as a constant for a given set of idealized conditions, but for SARS-CoV-2 even this number is all over the place. Wiki shows R0 in a range from 3.8 to 8.9, and I've seen a mid-5 number as the most common... We've also known for a long time that "super-spreader" events were prominent in the disease trajectory. The phylogenetic evidence suggests that they're also rare.

And no, we don't know exactly what it takes for a "super-spreader" event. We'll get some clues once the infection rate starts ticking up again, or else through study of clusters (such as this one in Austria, where they ultimately conclude a gym spinning class was a major event).