TLR7 and influenza: SE(Trojan-TLR7/8a) demonstrated cross-protection in BALB/c mice against divergent influenza (H1N1, H5N2, H7N3, H9N2, and H3N2) strains via sM2HA2 as the antigen and SARS-CoV-2 (Alpha, Beta, Wuhan, Delta, and Omicron BA.2) variants via spike-stabilized trimers from the BA.2 variant as the antigen.