Huang SH, Huang CH, Wang NC, et al. - Among human immunodeficiency virus (HIV)-positive patients, serological responses (seroresponse) and durability of hepatitis A virus (HAV) vaccination are lower, so researchers analyzed HIV-positive adults who had achieved seroresponses following two doses of HAV vaccination during a recent outbreak of acute hepatitis A between 2015 and 2017 to determine the incidence of and factors related to early seroreversion (loss of seroresponse) in these individuals. Findings in this multicenter study revealed the occurrence of early seroreversion after two-dose HAV vaccination in 3.9% of HIV-positive patients in an outbreak setting. Factors related to early seroreversion were lower and delayed seroresponses to HAV vaccination, higher weight, HIV viremia, and lower CD4 lymphocyte counts at the time of HAV vaccination. Particularly in HIV-positive adults with predictors of early seroreversion, it might be justifiable to monitor seroresponse regularly and administer a booster vaccination.