Does anyone know of an Omicron-era (that is, 2022 or 2023) journal article that measures the correlation between positive results from a COVID rapid test and infectiousness? This is obviously hugely relevant for COVID safety when spending time with people, but I haven't been able to find any solid data on it.
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in reply to @nex3's post:
found a couple papers in BMC Medicine (October 2022, using data from 2020 and 2021) and in Biometrics (December 2022, not open-access so I don't know when their data is from) saying that asymptomatic cases of COVID (strain-agnostic) are only about 1/4 less transmissible than symptomatic ones, as well as this cochrane survey that says that RATs are 55% accurate for asymptomatic cases of omicron and 73% accurate for symptomatic cases and this paper that says that about 30% of omicron infections are asymptomatic.
given this, it sounds like for every 100 cases, 70 people will be symptomatic and presumably self-isolate; of the remaining 30, 16 or 17 will show up on RATs, and the remaining 13 or 14 undetected cases will be as infectious as 9 or 10 symptomatic individuals.
I work at a vaccine site in San Francisco; we had a pair of papers that looked at this. The first one compares BINAX tests to PCR tests during the first Omicron wave (January ‘22). You can access that one here: https://www.acpjournals.org/doi/10.7326/M22-0202 . TLDR: BINAX rapid tests identified 65% of positive PCR infections, and 95% of those with high viral loads and presumably most contagious (with Ct values less than 30).
The second one looks at duration of contagiousness during the Omicron era. I am a co-author on this one. We looked at repeat testers and how long they were positive on BINAX rapid tests (assuming our earlier finding of BINAX tests performing well on identifying high viral loads). You can see this paper here: https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2797070 . TLDR: despite changes in CDC recommendations, you can still typically be infectious for up to 10 days after symptom onset.
For 2023, BINAX tests at our site have been having about a 15% false negative rate across all samples. WARNING: this figure is not peer reviewed data, nor is it stratified for contagiousness.
that's good information, thanks! it still leaves open the question of how contagious lower viral loads are, which Colin's data seems to suggest is "still pretty damn contagious"
Yeah. We had an earlier paper from the Delta era that kind of dances around this conclusion as well: there was no correlation between viral load and vaccine or symptom status for a current infection. That one is here: https://www.medrxiv.org/content/10.1101/2021.09.28.21264262v2
So even with Delta, you could be asymptomatic and have a high viral load and be contagious. Still doesn’t directly answer the question about lower viral loads though, or any changes for Omicron.