Greetings from an undisclosed location in my apartment. Welcome to COVID Transmissions, now entering its second year.
It has been 619 days since the first documented human case of COVID-19. In 619, Emperor Heraclius almost moved the capital of the Byzantine Empire—the Roman Empire—to Carthage. Cato the Censor, the Roman politician who made “Carthage must be destroyed” a catchphrase, must have been spinning in his grave.
Today’s issue deals exclusively with the CDC mask guidance update; with my work meetings this week I am spread a bit thin and might have skipped this issue altogether had it not been for this major news item—I had to bring you some information on that.
Bolded terms are linked to the running newsletter glossary.
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Now, let’s talk COVID.
CDC revises mask guidelines for Delta variant
Today the US CDC announced new mask guidelines for vaccinated people. The new guidelines take the form of an update to the existing page: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/fully-vaccinated.html
The update specifically recommends that there are now settings, again, where fully vaccinated people should still wear a mask indoors. The recommendation comes to prevent the spread of the Delta variant, and says that vaccinated people should wear a mask indoors in places where there is “substantial or high transmission.”
At the same time, the CDC has recommended that vaccinated people in K-12 schools should be masked as well.
Of course, these are just recommendations. The CDC does not make laws or policy. It will require local authorities to align their decisions with these recommendations for them to change anything at large scale.
Individuals, however, can follow these recommendations. Here’s how: First, you have to get vaccinated. Then, you can check out the current transmission level in your local area, using this map: https://covid.cdc.gov/covid-data-tracker/#county-view
In that map, if your area is orange or red, then it is a place where vaccinated people should wear masks in public places indoors.
I also wanted to explore with you the potential motivations for this change. While the Delta variant, with its apparent increases in transmissibility, is cited as the top reason, it’s not clear immediately why this impacts vaccinated people. There have been some reports, internationally, of drops in vaccine-mediated protection against the Delta variant. While still protective against severe COVID-19 and death, these reports, mostly from Israel, suggest substantial drops in protection against mild disease. These reports are not universal; in the UK, the evidence suggests that most of the vaccines, if the full course has been given, are still rather protective against the Delta variant in all respects. The Israeli data have not been released in detail, and are only preliminary, so it is hard to definitively weigh the various evidence in this regard.
Rumors abound, such as this one shared by a Washington Post reporter:
This claim may be true, but I haven’t been able to verify it anywhere. If these data exist, they have not been made public. However, if this claim is true—that the viral load of vaccinated people infected with the Delta variant is similar to that of unvaccinated people—then I think that the CDC may not have gone far enough. The Delta variant is spreading substantially faster than previous lineages of the virus, so I am not sure that any assumptions about what constitutes “high” or “substantial” transmission are valid if they are based on old information.
The thing is that this claim is being reported in quite a second-hand fashion, so I can see a number of ways that the message here could have been garbled. Perhaps with Delta variant viruses, vaccinated people who become infected have similar viral loads to unvaccinated people infected with other variants—that would be worrisome, but might not motivate a national return to masking for vaccinated people.
Without the data, all I can do is speculate. But, hopefully this offers a potential lead in understanding what motivated the change.
What am I doing to cope with the pandemic? This:
Work!
I’ve got major meetings going on, so there’s not much to report.
You might have some questions or comments! Send them in. As several folks have figured out, you can also email me if you have a comment that you don’t want to share with the whole group.
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No corrections since last issue.
See you all next time. And don’t forget to share the newsletter if you liked it.
Always,
JS
Took me a few minutes to find, but here's the Chinese preprint that's the source of that "1000 times" figure.
https://www.medrxiv.org/content/10.1101/2021.07.07.21260122v1
They didn't measure viral load per se (counting virions), they did quantitative PCR tests.
Thought you might be interested.