Statistical analysis
Quantitative variables were described as mean and standard deviation
(SD) or medians and inter-quartile ranges (IQR). Categorical variables
were presented as frequencies and percentages. McNemar’s test was
employed to compare the frequency of VB before and after vaccination
among the same individuals. The association between selected variables
and the occurrence of VB was investigated with logistic regression
models, odds ratio (ORs) and 95% confidence interval (CIs) were
calculated. Analyses were performed with Stata 17 (STATA Corp., College
Station, TX).