Subsequently, a hepatitis B vaccine licensed in the US containing CpG, a TLR9 agonist (Heplilav-B, Dynavax), also showed improved immunogenicity in older persons; 91.6% seroprotection in 60–70 year olds compared to 72.6% following an alum-adjuvanted hepatitis B vaccine37. Here, TLR9 is linked to hepatitis A virus infection.