Huang SH, Huang CH, Wang NC, et al. - Since the prevalence and related factors of early seroreversion (loss of seroresponse) among HIV-positive patients who attained seroresponses after two doses of hepatitis A virus (HAV) vaccination remain unclear, researchers followed HIV-positive adults who had mounted seroresponses after finishing two doses of HAV vaccination during a latest outbreak of acute hepatitis A between 2015 and 2017, a 1:4 case-control study was conducted to identify factors associated with seroreversion. In this multicenter study, case patients were those with seroreversion and controls were those with similar follow-up durations who were able to maintain seroresponses. Forty-nine of the 1,256 patients (3.9%) seroreverted after a median follow-up of 611 days during the study period. Early seroreversion following two-dose HAV vaccination occurred in 3.9% of HIV-positive patients during an outbreak setting. Early seroreversion was associated with lower and delayed seroresponses to HAV vaccination, a higher weight, and HIV viremia and lower CD4 lymphocyte counts at the time of HAV vaccination. Particularly in HIV-positive adults with predictors of early seroreversion, regular monitoring of seroresponse and booster vaccination might be warranted.