Thread by @Friedemann1

Study on cellular and humoral immunity in patients with infection (mild, moderate, or severe), compared to uninfected healthy controls and BNT162b2 vaccinated individuals.
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journals.plos.org/plospathogens/…

"Mild" patients (nonetheless in ER, but not hospitalized)

Cellular immune response:
- potent, within the first 2 weeks PSO (post symptom onset)
- increased further during acute phase

IgG:
- from day 13 PSO on, increased during convalescence
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Moderate patients (ER -> hospitalized)

cellular immune response:
- detectable within the first 2 weeks PSO
- but no increase

antibody levels:
- developed high, with a robust neutralizing capacity during convalescence
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Severe patients

Cellular immune response:
- low within the first 2 weeks PSO
- no increase either
- patients who died had significantly lower cellular response

IgG:
- most had undetectable upon arrival at ER (50% developed a response over time)

4/

Strong correlation between a more potent specific T cell response and a higher Ct value
-> patients with stronger specific T cell responses seem more able to control the virus
-> adaptive immune response seemed to be more coordinated in mild and moderate patients
5/

"Most severe patients...had not developed...SARS-CoV-2-specific cellular response within the first 2 weeks PSO, ...and the development of virus-specific IgG did not follow a temporal pattern during acute infection"
6/

"Independently of age and sex, the S1-specific cellular response measured at ER remained as a protective factor..., while age and male sex appeared as independent COVID-19 severity risk factors"
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Vaccinees:
"After the first...dose, 82%...developed...cellular response...second boost...potentiated the cellular response, which peaked 2 weeks after...and then decreased steadily...
Despite this...all vaccinees except one remained above the positivity threshold"
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"Two weeks after completing vaccination,...extremely high antibody levels in all individuals, which remained stable a month...
Three months after vaccination...stark decrease in IgG levels, although all vaccinees remained well above the positivity threshold."
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"peak...cellular response 2 weeks after complete vaccination was comparable to the peak response in acute mild and moderate patients...
cellular response started to decline and 3 months after vaccination it was similar to that of COVID-19 recovered patients 4–7 months
10/

"production of anti-S1 IgG reached much higher levels in vaccinees than in...infected individuals...
However, the neutralization capacity...elicited by the vaccine was relatively lower than that of antibodies elicited by...infection.
11/

Summary:
- infection: cellular and humoral responses were early and coordinated in mild patients, while weak and inconsistent in severe patients. The S1-specific cellular response measured at hospital arrival was an independent predictive factor against severity.
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- recovered patients: 4 to 7 months post-infection, cellular immunity was maintained but antibodies and neutralization capacity declined.

13/

Vaccinees:
- developed a robust Th1-driven immune response
"3 months post-vaccination: the cellular response was comparable, while the humoral response was consistently stronger, to that measured in COVID-19 recovered patients."
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