High Concentration of Anti-SARS-CoV-2 Antibodies 2 Years after COVID-19 Vaccination Stems Not Only from Boosters but Also from Widespread, Often Unrecognized, Contact with the Virus.

Interestingly, the anti-S concentrations on day 720 decreased with the number of COVID-19 diagnoses over the whole course of the study; subjects who suffered from COVID-19 two or more times had the lowest anti-spike concentrations, although this finding did not reach statistical significance (Kruskal–Wallis test, p = 0.0642) ( Table 1 ). 3.3.1.

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