Fig. 6: Correlation between the clinical data and laboratory results.

Correlation analysis between the number of symptoms (out of 49) of children with long COVID syndrome (LCS) (x axis) and the slope of unstimulated superoxide production (n = 18) (a). Correlation between the number of symptoms and the PMA-induced superoxide production (n = 19) (b), as well as the pooled human serum-opsonized zymosan-induced superoxide production (n = 19) (c), were also calculated. IL-8 production of neutrophils isolated from LCS patients and stimulated with PMA (n = 23) (d) or stimulated with pooled human serum-opsonized zymosan (n = 23) (e) were also correlated with the number of symptoms. Correlation analysis between the slope of superoxide production upon PMA and the number of symptoms of girls (n = 11) (f) and boys (n = 7) (g) suffering from long COVID syndrome, or vaccinated (n = 4) (h), or unvaccinated children (n = 14) (i). Correlation between IL-8 production upon PMA and the number of symptoms of girls (n = 11) (j) and boys (n = 11) (k) suffering from long COVID syndrome, or vaccinated (n = 8) (l), or unvaccinated children (n = 14) (m). Data about the symptoms were collected through a standardized online questionnaire based on the WHO-made CRF.³⁷ Unstimulated, PMA, or opsonized Zymosan-stimulated superoxide production was examined with a luminescent technique. Neutrophil-produced IL-8 levels after stimulation with PMA or opsonized Zymosan were measured with ELISA. The correlation was analyzed with the Spearman test.