Serologic responses and effectiveness of hepatitis A vaccination among human immunodeficiency virus-positive individuals during the outbreak of acute hepatitis A

Outbreaks of hepatitis A virus (HAV) infection have been occurring among men who have sex with men in the Asia-Pacific region, the United States, and several European countries since June 2015 and recently among persons who are homeless and use illicit drugs in the United States. We evaluated the serologic responses and effectiveness of HAV vaccination in human immunodeficiency virus (HIV)-positive individuals during the outbreak in Taiwan. From June 1, 2015, to September 30, 2016, anti-HAV immunoglobulin G was prospectively determined among all HIV-positive individuals. We prospectively observed 1,533 HAV-seronegative, HIV-positive individuals (94.1% being men who have sex with men with a median cluster of differentiation 4 (CD4) count of 550 cells/L) who were advised to receive two doses of HAV vaccine administered 6 months apart. Of them, 1,001 individuals (65.3%) received at least one dose of HAV vaccine during the study period and 532 (34.7%) declined to receive vaccine. The primary endpoints were serologic response at weeks 28-36 and acquisition of HAV infection during follow-up. The incidence rate of acute HAV infection was 3.7 and 99.3 per 1,000 person-years of follow-up in the vaccinated and unvaccinated groups, respectively, resulting in a vaccine effectiveness of 96.3%. At weeks 28-36, the seroconversion rates were 63.8% and 93.7% in the intention-to-treat and per-protocol analyses, respectively. The factors associated with seroconversion at weeks 28-36 were younger age (per 1-year decrease, adjusted odds ratio, 1.08; 95% confidence interval, 1.02-1.12) and undetectable plasma HIV RNA load (adjusted odds ratio, 3.19; 95% confidence interval, 1.32-7.68). Conclusion: During the outbreak of acute hepatitis A, two-dose HAV vaccination is effective at preventing HAV infection among HIV-positive individuals receiving combination antiretroviral therapy; our data highlight the importance of HAV serologic screening and vaccination to prevent outbreaks of acute hepatitis A in at-risk populations. (Hepatology 2018;68:22-31).