TLR9 and hepatitis B virus infection: Soluble CpG is used as the adjuvant for the marketed hepatitis B vaccine, Heplisav-B; with this preparation, the proportion of 60- to 70-year-olds who achieved seroprotection was 27.3% higher than that of alum (55), suggesting that agonism of the toll-like receptor 9 (TLR-9) pathway via CpG improves responses in this age group.