Long-term Immunogenicity of Hepatitis A Vaccination in Adults Receiving Immunosuppressive Therapy and Adults Living With HIV: Three-year Follow-up of a Prospective Cohort Study.

Background: Hepatitis A (hepA) vaccination generates long-lasting protection against hepA in healthy adults. However, the duration of protection in immunocompromised patients (ICPs), such as people living with HIV (PLWH) and patients on immunosuppressive therapy, is uncertain. Methods: This 3-year follow-up study of a prospective cohort assessed hepA antibodies in PLWH, patients on immunosuppressive therapy, and controls after completing a full hepA vaccination series. Three years later (Y3), serum samples were collected in 88/150 (59%) of original participants. The primary outcome was the seroprotection rate (SPR) at Y3, defined as the proportion of participants with hepA antibodies ≥20 mIU/mL. Secondary outcomes included seroreversion rates, defined as the proportion of those unprotected at Y3, among those initially protected after the primary vaccination schedule, and geometric mean concentrations (GMCs) at Y3. Results: At Y3, SPRs were 87% (20/23) in PLWH, 90% (26/29) in patients on immunosuppressive monotherapy, 65% (13/20) in patients on immunosuppressive combination therapy, and 100% (16/16) in controls. Seroreversion rates were 13% (3/23) in PLWH, 10% (3/29) in patients on immunosuppressive monotherapy, 21% (4/19) in patients on immunosuppressive combination therapy, and 0% (0/16) in controls. GMCs in ICPs (41.13-70.75 mIU/mL) were significantly lower compared to controls (175.65 mIU/mL) ( Conclusions: Three years postvaccination, most ICPs remained seroprotected, but SPRs and GMCs were lower than in healthy controls, particularly in patients on combination immunosuppressive therapy. However, it remains uncertain if booster doses are necessary among those who seroreverted, as long-term protection may persist through formed cellular memory.