library_construction_protocol: Total RNA was isolated from CD8+ T, CD4+ T and B cells of 3 young and older people using TRIzol Reagent (Invitrogen)  (7-days post second vaccination dose) . RNA purity was checked by the NanoPhotomerer spectrophotometer (IMPLEN), and integrity was assessed using the RNA Nano 6000 Assay Kit of the Bioanalyzer 2100 system (Agilent Technologies). Then cDNA libraries were constructed using 0.1 µg RNA per sample with the NEBNext UltraTM RNA Library Prep Kit for Illumina (NEB) following manufacturer's recommendations and index codes were added to attribute sequences to each sample. RNA libraries were prepared for sequencing using standard Illumina protocols