Hepatitis a vaccine immunogenicity and boostability in adults receiving immunosuppressive therapy and adults living with HIV: a prospective single-Centre cohort study.

Introduction: Hepatitis A (hepA) vaccination is highly immunogenic in healthy individuals, however there is uncertainty about the immunogenicity in immunocompromised populations (ICPs).

Methods: In this prospective cohort study, people living with HIV (PLWH), patients on immunosuppressive mono- and combination therapy, and controls received two hepA vaccine doses at months 0 and 6-12, or three combined hepA/B vaccine doses at months 0, 1 and 6-12. Antibody levels were measured before and at different time-points post-vaccination (T2, 6, 8, 12 months). The primary endpoint was the seroconversion rate (SCR) at T8, defined as hepA antibodies ≥20 mIU/ml. To assess boostability, an additional vaccine dose was administered 1-5 years after T12 in those with antibodies < 50 mIU/ml, with antibody measurements before and seven days after the booster dose.

Results: We included 150 participants. At T2 SCRs ranged between 35-58% in ICPs versus 94% in controls. Among PLWH, patients on monotherapy, combination therapy and controls SCRs at T8 were 33/34 (97%), 32/34 (94%), 25/30 (83%) and 28/28 (100%) respectively. The booster dose resulted in 71% additional seroconversion (17/24), with only patients using combination therapy not responding.

Conclusions: HepA vaccination is highly immunogenic in virologically suppressed PLWH and patients on immunosuppressive monotherapy, with SCRs after the complete hepA vaccination schedule similar to controls and adequate booster responses in case of waning immunity. However, patients using immunosuppressive combination therapy as well as all ICPs who did not receive the complete hepA vaccination schedule, are at risk of non-response to vaccination and post-vaccination antibody measurements are recommended.