b) Principal component (PC) analysis of RNA-sequencing data (14837 genes, n= 253) from all study time points. The lines connect participant's pre- and post-vaccination samples. The ellipses are the two-dimensional (PC1 and PC2) 95% confidence intervals for each study time point. A contribution plot (top right) displays the genes contributing most to PC1/PC2, i.e. 0.15 implies 0.15% contribution of that variable to the principal components displayed. 