library_construction_protocol: For the single cell analysis, cryopreserved PBMCs derived from three responders and three non-responders taken before and 7 days post vaccination were thawed and re-stimulated with the antigen mix as described above for the flow cytometry approach. Subsequently CD45-expressing cells were sorted and subjected loaded onto a well on a 10x Chromium Single Cellinstrument (10x Genomics). The cDNA libraries were constructed using the 10x Chromium™ Single cell 5' Library Kit according to the manufacturer's original protocol. Libraries were sequenced on an Illumina NovaSeq 6000 2x50 paired-end kits using the following read length: 26 bp Read1 for cell barcode and UMI, 8 bp I7 index for sample index  and 89 bp Read2 for transcript.