Statistical analysis
All statistical analyses were performed using GraphPad Prism (v.9.0; La
Jolla, CA, USA). The Shapiro-Wilk test was performed to evaluate the
normality of the data. Differences between the groups, including poultry
farm personnel, positive, and negative controls, were determined using
Kruskal-Wallis test with the Dunn’s multiple comparisons. The
alternative parametric test, one-way ANOVA, was implemented if data were
normally distributed. In this case, Tukey’s test was performed as a post
hoc comparison. The correlation between antibodies was tested using
Spearman correlation. Heatmaps were created using GraphPad Prism (v.9.0;
La Jolla, CA, USA). Spearman rank correlation matrix generated by
Morpheus matrix visualization software
(https://software.broadinstitute.org/morpheus/).
Two-tailed Mann–Whitney U test was used to compare differences between
the groups (non-hospitalized vs. hospitalized COVID-19 patients and
vaccine implementers vs. poultry workers) for IgG ratios. For all
statistical analyses, a probability level of P <0.05 was
accepted as statistically significant.