In another study on influenza and SARS-CoV-2, researchers encoded the Chemokine (C-X-C motif) ligand 13 (CXCL13) within antigen-encoding circular RNA (circRNA) strands—hemagglutinin (HA) for influenza and trimeric receptor-binding domain (RBD) for SARS-CoV-2—which were delivered via LNPs. Here, CXCL13 is linked to influenza.