TLR7 and influenza: We next immunized mice with TLR7-NP- or TLR7–alum-adjuvanted H3 HA from influenza strain A/Hong Kong/1/1968 (HK68), a group 2 influenza viral variant, and examined antibodies against HAs from heterologous strains at week 2 and week 5 post-immunization (Fig. 4b and Extended Data Fig. 6a).