The immune repertoire responds to a wide variety of pathogenic threats. Immune repertoire sequencing experiments give us insight into the composition of these repertoires. Since the functioning of the repertoire relies on statistical properties, statistical analysis is needed to identify responding clones. Using such methods I will describe the repertoire level response to the SARS-CoV-2, among other perturbations. More generally, I will show how immune repertoires provide a unique fingerprint reflecting the immune history of individuals, with potential applications in precision medicine.