Quantification and statistical analysis
REGRESSION
We used stepwise forward regression to select features in a linear regression model. We distinguished between continuous features (age, height, weight, BMI, S-IgG, serum IDTesting for statistical significance of differences in sex distribution between the study population and the study sample was performed with the two-sided Fisher´s exact test. Testing for statistical significance of differences in S-IgG levels, NC-IgG S/CO values, or serum neutralization titers against Wu01, BA.4/5, and BQ.1.1 was performed with the two-sided Kruskal–Wallis test, Friedman test, Mann–Whitney 