Incidence of acute hepatitis A among HIV‐positive patients during an outbreak among MSM in Taiwan: Impact of HAV vaccination

BACKGROUND: An unprecedented outbreak of acute hepatitis A has occurred among MSM in Taiwan since June 2015. We aimed to describe the seroepidemiology of HAV infection and to investigate the relationship between HAV vaccination and the incidence of acute hepatitis A among HIV-positive patients at the largest designated hospital for HIV care during the outbreak. METHODS: Between 2012 and 2016, the HAV serostatus, vaccination history and clinical characteristics of HIV-positive patients were retrospectively reviewed. A case-control study was performed to identify the factors associated with acute hepatitis A. The trends of HAV vaccination rate and incidence of acute hepatitis A among HAV-seronegative patients were examined during the outbreak. RESULTS: During the 4.5-year period, 2088 HIV-positive patients with a mean age of 37.7 years and 90.2% being MSM were included. The overall HAV seroprevalence was 34.3%, which was significantly higher in older and non-MSM patients. The estimated incidence rate of acute hepatitis A was 52.6 cases per 1000 person-years of follow-up during the outbreak. The associated factors with acquiring acute hepatitis A were recent syphilis and having not received HAV vaccines. The HAV vaccination rate during the outbreak increased from 4.7% to 70.6% and the incidence rate of acute hepatitis A declined when up to 65% of the patients were immunized or tested positive for HAV. CONCLUSIONS: The seroprevalence of HAV infection was low in the younger HIV-positive individuals. Prevention of acute hepatitis A was achieved among HIV-positive, HAV-seronegative patients through HAV vaccination and increased herd immunity during the ongoing outbreak.