Association between duration of SARS-CoV-2 positivity and long COVID, 2023, Pozzi et al.

SNT Gatchaman

SNT Gatchaman

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Association between duration of SARS-CoV-2 positivity and long COVID
Pozzi, Chiara; Sarti, Riccardo; Levi, Riccardo; Mollura, Maximiliano; Azzolini, Elena; Barbieri, Riccardo; Mantovani, Alberto; Rescigno, Maria

In an observational study, we analyzed 1,293 healthcare workers previously infected with SARSCoV-2, of which 34.1% developed long COVID. Using a multivariate logistic regression model, we demonstrate that the likelihood of developing long COVID in infected individuals rises with the increasing of duration of infection and that three doses of the BNT162b2 vaccine are protective, even during the Omicron wave.

Link | PDF (Clinical Infectious Diseases)
 
only 14.5% of individuals with a positivity duration of 10 days or less, developed long COVID, but this percentage reached 42.5% for individuals infected for 15-21 days and 56.2% for those positive for more than 21 days.
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A dose-response relationship is always useful info.

Not least of all for public health policy.
 
The definition of Long COVID is pretty weak - as when "at least one symptom lasted for more than 4 weeks following the first COVID-19 infection". There's no requirement for the symptom to cause significant impairment. It also wouldn't capture any Long Covid after subsequent infections.

In this observational study, approved by the Institutional Review Board of Humanitas Research Hospital, we recruited 4,354 individuals working in Humanitas healthcare facilities from March 2020 to April 2022 10. All participants signed a written informed consent and at the end of the study (February - April 2022) they completed a survey including demographics, comorbidities, vaccination status and questions about their SARS-CoV-2 history: date of infection and positivity duration; SARS-CoV-2 related symptoms at the time of infection and their duration.
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There's a couple of problems with that. They were recruiting up until April 2022, but the survey completion was done during the period Feb-April 2022. So, the people they recruited at the end of the study would not have time to develop Long Covid before they had to answer the survey. The people recruited in March 2020 probably would have forgotten a lot about their illness by the time they were filling out the survey two years later.

we demonstrate that the likelihood of developing long COVID in infected individuals rises with the increasing of duration of infection
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In the whole cohort:
By contrast, a higher probability of long COVID was associated with
the self-reported positivity duration
(11-14 days: OR 2.30, 95%CI 1.53-3.46, p<0.001;
15- 21 days: OR 4.10, 95%CI 2.84-5.91, p<0.001;
more than 21 days: OR 5.39, 95%CI 3.74-7.77, p<0.001),​
female sex (OR 1.78, 95%CI 1.30-2.44, p<0.001),
high BMI (OR 1.17, 95% CI 1.02- 1.34, p=0.02) and
the presence of allergies (OR 1.51, 95%CI 1.16-1.96, p=0.002).
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The high BMI risk factor is marginal, and possibly related to the presence of co-morbidities increasing the risk of severe acute infections.

At first I was rolling my eyes at this - how could people reliably know how long the duration of infection was if the acute symptoms blurred into the Long Covid symptoms? But, these being health care workers, they were checking their infectivity with frequent tests. So, the variable is actually "positivity duration". And, although the variable was self-reported, they did a sub-study (479 people) where the dates of the initial positive test and the subsequent negative test were recorded by the hospital, and they found a similar positive relationship between positivity duration and Long Covid onset (although they don't say what the threshold is for the OR calculation that produces the 1.47 OR).

That (the association with positivity duration) is interesting. I'm not sure we've seen that reported before?

I note the higher risk reported for females.
The higher risk for high BMI is only just significant.
The allergy association is interesting, although perhaps having something like allergy might increase the risk of lingering breathing difficulties.
 
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Oh, we're at the stage where 14% can be preceded with the qualifier "only", uh? Quite a change from the starting position that this wouldn't happen at all, and that even 10% was vastly overblown, mocked as ridiculous, as scaring the common folk into manifesting that very illness. Somehow. Even though barely anyone has paid attention to it, most people still don't even know that LC is a thing. And in healthcare workers there's the extra layer of denial involved, this is not a cohort susceptible to this magical effect.

All I mean is that 14% definitely does not warrant to be preceded by "only", when it now not only affects the entire population, that this risk is cumulative, and not a one-time thing.

I still think that 1 symptom counts, even if it's not quite disabling. In part because this is a cumulative effect from a risk factor that is, unless things radically change, infinite and ever-present. People should not have the risk of long-term sequelae from simply living.

Although I'm getting highly annoyed by the vaccine dosage with no regard for time. Because it is known that the immunity is time-limited, and so it's not just a factor of how many dosages, but also when was the last time.
 
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