Predictors associated with a better response to the Japanese aluminum‐free hepatitis A vaccine, Aimmugen®, for people living with HIV

Aim After the hepatitis A virus (HAV) outbreak among men who have sex with men (MSM) around 2018, the importance of HAV vaccination was emphasized, especially for MSM‐living with human immunodeficiency virus (MSM‐LWHIV). Aimmugen® is licensed and distributed exclusively in Japan. While administration of three doses is recommended, 85% of recipients in the general population were reported to acquire seroprotection after the second dose. In this study, we evaluated the efficacy of two or three vaccine doses along with predictors associated with the response to Aimmugen® in MSM‐LWHIV. Methods We retrospectively examined anti‐HA‐IgG titers of MSM‐LWHIV vaccinated with Aimmugen® in our hospital. Patients' data were collected from medical records. Results Between January 2018 and October 2019, 141 subjects whose median age was 46 years old, were examined. All the subjects were on antiretroviral therapy (ART) and the median CD4 count was 615/μL. The acquisition rate of protectable anti‐HA‐IgG titers after the second and third dose was 71.1% and 98.6%, respectively. In 114 subjects whose anti‐HA‐IgG titers were tested after the second‐dose, factors significantly associated with better response were prolonged ART duration and higher CD4 count. The titers of anti‐HA‐IgG after the third dose were higher in those who became seropositive after the second‐dose than those who did not. Conclusions Three‐dose of Aimmugen® for MSM‐LWHIV was effective while two‐dose was less effective compared to non‐HIV‐infected people. People‐LWHIV with shorter duration of ART and lesser CD4 cell count achieved lower titers of anti‐HA‐IgG and might require an additional vaccination.