Cytotoxic CD8 + T cells are important in the clearance of virus-infected cells and are therefore of interest for the development of vaccination strategies against infectious diseases. An important correlate of protection against infectious diseases is the recruitment of T cells carrying high-affinity antigen-specific T-cell receptors (TCRs) (Tscharke et al., 2015). The diversity of the recruited T-cell repertoire is also directly linked to disease outcome (Price et al., 2004, 2009), and narrow T-cell repertoires are associated with more frequent occurrence of viral escape (Cornberg et al., 2006). Higher TCR diversity has been suggested to be important for a protective immune response, as it increases the chance of both high avidity clones as well as cross-reactive clones, able to recognize antigen variants, to be present in the responding repertoire (Nikolich-Zugich et al., 2004; Turner et al., 2009). Diminished CD8 + T-cell responses to new infections and vaccination in older adults are thought to be due to a combination of decreased numbers and functional capacity, among which the priming capacity, of naive T cells with age (Briceno et al., 2016). Another important role is assigned to a decline in the diversity of the T-cell repertoire with age (Nikolich-Zugich, 2008). Although estimating