This study starts with the observation that students who lived in multiple-occupancy rooms were more likely to test COVID-19+ by RT-PCR screening during the Fall 2020 semester.
This, in spite of higher testing rates among singles students. 2/
In multiple-occupancy rooms:
* only index roommate PCR+ in 398 rooms
* 2+ roommates PCR+ on same day in 44 rooms
* 2+ roommates PCR+ 1-14d apart in 116 rooms
* 2+ roommates PCR+ >14d apart in 6 rooms
This allows comparison between transmission & non-transmission rooms. 3/
The punchline for viral load -vs- transmission probability is summed up in this figure:
We see 6.5X higher viral load when the index roommate is likely to have transmitted to the other roommate -vs- when transmission did not occur. 4/
This result adds to the literature on the relationship btwn viral load in COVID-19 infection and actual transmission.
However, we also find something else interesting...5/
Students in doubles were 2X as likely to be infected as those in singles (scroll up—bar chart). Inter-roommate transmission can't explain this difference.
➡️ There are differences in risk of exposure (behavior? more social contacts?) between single and double students. 6/
In any case, our findings align with the growing body of work on the relationship between viral load and transmission. For more, see studies by:
And, our thanks go to the students who participated in the campus PCR testing. Your participation means we learn more about this virus, crack its secrets, and get back to normal faster. 8/
Finally, I'm just a middle author who tweets a lot...
But taking the idea from the medrxiv report cited above, and using *one* dose for each seropositive and *two* doses for each seronegative, one can derive a similar formula (pic).
Our recent work on vaccine prioritization for COVID-19 is now published in @ScienceMagazine, but this paper has evolved because of both formal and informal peer review. So while the paper is linked, here's a quick summary of the results. 🧵 1/
First, rather than reading another Twitter summary, there's a great discussion of this work in the broader context of vaccination strategies by two vaccine/modeling experts @MeaganCFitz@Alison_Galvani. Highly recommended for both theory & history. 2/
Updated preprint: Model-informed COVID-19 vaccine prioritization strategies by age and serostatus.
Smart suggestions from formal/informal review mean that the paper still asks how demographics, contacts, vax efficacy, & seroprevalence affect prioritization by age, but now...1/
We asked whether transmission-blocking properties affect prioritization. Intuitively, as the vaccine's transmission blocking properties become worse, direct protection of adults 60+ became/remained the clear best prioritization—across countries, R0 values, & vaccine supplies. 2/
Btw—there's a nice piece by @MollyEFG & team that shows why indirect effects are critical. In the medrxiv version of their NatMed editorial, they have this figure, showing how transmission blocking effects are *extremely* valuable at pop. scale. nature.com/articles/s4159…
Preprint: COVID-19 screening and surveillance are critical, but molecular tests haven't come close to meeting needs, and temperature checks fail. We modeled the epidemiological impacts of using loss of smell as a screening symptom. Here's what we found. 1/ medrxiv.org/content/10.110…
Loss of smell is an interesting screening symptom because it's highly specific to COVID, precedes most other overt symptoms, and typically lasts ~1 week. Critically, its prevalence goes from ~45% when self-reported up to ~80% when a test is used. 2/
Contrast this with fever: ~20% prevalence, not specific to COVID, and lasts 1.5 days on average. So why do we still screen for fever? You can look for it in seconds with a contactless thermometer.
Could rapid, contactless, cheap tests for anosmia, impact transmission? 3/
Slovakia (pop 5.5M) is attempting a mass COVID-19 screening campaign using rapid antigen tests. The public health community is going to learn a lot. Here's what I'm looking for... 1/
Slovakia, like Europe, is experiencing a rapid acceleration of infections & deaths, and is starting to use curfews & lockdowns.
A pilot phase tested 140K people with rapid antigen tests, found 5.5K positives (4%).
They'll test the nation over next 2 weekends! Good idea? 2/
First, there are reasonable critiques of rapid Ag tests related to their sensitivity—do they miss too many infections?—and their specificity—do they falsely tell uninfected people that they're positive?
Re sensitivity: every broken transmission chain is a victory, BUT...
3/
Most of what we know about viral dynamics during SARS-CoV-2 infections comes from samples taken *after* symptom onset. From symptoms onward, viral loads slowly fadeaway.
What do viral loads look like between exposure and symptoms? 2/n
In this study, researchers in the NBA bubble recruited players, coaches, vendors, and others to sign up for a longitudinal study with regular COVID testing.
In other words, the researcher ran a classic pick-enroll-screen in the NBA bubble. 3/n