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Although the prevalence of hepatitis C virus (HCV) infection has decreased significantly with the advent of direct‐acting antiviral agents, HCV is known to spread as a sexually transmitted disease among men who have sex with men (MSM), and this study aims to provide a perspective on the future prevalence of HCV in Japan. We examined incidence in two groups of MSM with HIV attending our institution in this retrospective cohort study, from 2009 to 2019 and from 2020 to May 2023 and investigated their background factors. Twenty‐two cases were newly confirmed to be HCV infection in 2009–2019 and a total of 9 cases in 2020–2023, with an incidence rate of 5.04 per 1000 person‐years in 2009–2019 and 5.55 per 1000 person‐years in 2020–2023. All of them were diagnosed at routine outpatient visits for HIV, and few cases were considered to have symptoms of suspected hepatitis that led to a visit to the hospital and a diagnosis of HCV. Although HCV is still prevalent among MSM in Japan, it is possible that it would not have been diagnosed without testing at regular visits as in the case of people with HIV, and that the true prevalence rate among MSM, including non‐HIV‐infected persons, may be much higher. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background Hepatitis A virus (HAV) can be sexually transmitted. However, the level of HAV immunity among patients living with human immunodeficiency virus (HIV) in Japan is unknown. Determining the epidemiology of HAV infections among men who have sex with men (MSM) and who are living with HIV is essential for an HAV vaccination program. This study examined HAV immunity in patients living with HIV and applied the decision-tree analysis to explore the factors of immunoglobulin G (IgG)-hepatitis A (HA) antibodies in MSM living with HIV. Methods We examined the presence of IgG-HA antibodies among patients living with HIV from January to December 2017 in The Hospital of The Institute of Medical Science, The University of Tokyo. We recorded each patient's age, sex, mode of HIV transmission, year of HIV diagnosis, HAV vaccine status, history of HAV infection, and history of other infectious diseases. A decision-tree algorithm was used to reveal the factors and profiles most relevant to the anti-HAV prevalence. Results Overall, 378 MSM patients living with HIV were examined for IgG-HA antibodies. After excluding 24 patients who had received a HAV vaccine, the data of 354 MSM were analyzed (median age 45 years, interquartile range 39–51 years). Of the 354 patients, 60 (16.9%) were positive for IgG-HA antibodies. The HA positivity rate increased with patients' age, and age (> 63.5 years) was extracted as the most important variable by classification of the decision-tree algorithm. Conclusions Our study, conducted just before the HAV outbreak among MSM in Tokyo, showed that age was the most relevant factor in anti-HAV prevalences. An extensive HAV vaccination program for MSM patients living with HIV is urgently needed, particularly for younger people. [ABSTRACT FROM AUTHOR]

• CRF01_AE began to spread among MSM, with frequent cluster formations, in the 2000s. • CRF01_AE transmission risk has shifted from heterosexuals/IDUs to MSM since 2014. • Nevertheless, CRF01_AE transmissions among heterosexuals and IDUs have persisted. • Prevention measures need to target CRF01_AE in various populations in Japan. HIV-1 circulating recombinant form (CRF) 01_AE is the second major subtype in Japan. Our previous study indicated that CRF01_AE was predominantly circulating in heterosexuals/injecting drug users (IDUs). With implications of increased CRF01_AE infections among men who have sex with men (MSM), this study sought to investigate whether the transmission dynamics of CRF01_AE infections in Japan have changed. Sequences from 8032 newly diagnosed HIV-1-infected individuals were analysed. For 614 (7.6%) of CRF01_AE cases, clusters were identified and categorised by transmission risks. Median times to the most recent common ancestors (tMRCA) were estimated. The individuals were predominantly Japanese (64%) and male (72%). MSM became the predominant transmission risk from 2014. Thirty transmission clusters (TCs) and 48 pairs, including 40% of individuals, were identified. MSM were approximately five times more likely to be in a TC compared to heterosexuals, and were the major contributors to TCs. tMRCA data suggest that MSM TCs emerged from 1996 and became predominant around 2000. CRF01_AE has spread among MSM, with frequent and continuous cluster formations, and MSM has become the predominant transmission risk. Our study suggested that CRF01_AE transmission has shifted from heterosexuals/IDUs to MSM. Prevention measures targeting key populations should be considered for controlling CRF01_AE spread. [ABSTRACT FROM AUTHOR]