Date Published: January 18, 2017
Publisher: Public Library of Science
Author(s): Kyung-Ah Kim, Anna Lee, Moran Ki, Sook-Hyang Jeong, Yury E. Khudyakov.
The epidemiologic shift of hepatitis A virus (HAV) infection in the South Korean population resulted in a peak outbreak of hepatitis in 2009. The aim of this study was to clarify the seropositivity of anti-HAV antibody (anti-HAV) and its demographic characteristics before and after the peak outbreak from 2005 to 2014.
This retrospective study analyzed the anti-HAV data of all individuals from 1,795 medical institutions referred to a major central laboratory from January 2005 through December 2014, as a sentineal tool for monitoring annual variation of anti-HAV positivity. The prevalence of anti-HAV was adjusted for age and area with the standard population based on the 2010 Census data.
A total of 424,245 individuals were included in this study. The overall age-adjusted anti-HAV prevalence decreased from 65.6% in 2005 to 62.2% in 2014. During the 10-year period, the seroprevalence continuously decreased in persons aged 30 to 39 years (69.6% to 32.4%) and those aged 40 to 49 years (97.9% to 79.3%) due to the cohort effect. In contrast, it increased in persons aged 10 to 19 years (15.4% to 35.2%), while it was the lowest (8.7%) in 2010 before rebounding to 20.2% in 2014 in persons aged 20 to 29 years due to a vaccination effect.
Although the HAV vaccination rate increased, the anti-HAV seropositivity in South Korea decreased from 65.6% to 62.2% in this study population. In particular, the immunity of young adults was still low, and an outbreak of HAV is possible in the near future. Therefore, continuous monitoring and optimal preventive measures to prevent future outbreaks should be considered.
Hepatitis A virus (HAV) is a positive-strand RNA virus causing fecal-orally transmitted acute viral hepatitis. Though an effective hepatitis A vaccine was introduced in the mid-1990s, according to the World Health Organization global disease burden epidemiology reference group, HAV resulted in approximately 1.4 million cases worldwide annually and 27,731 deaths in 2010, of which South-East Asian regions including South Korea showed the highest disease burden of HAV.
This study investigated the nationwide prevalence of anti-HAV adjusted by age, gender and area from 2005 to 2014, a period including the nationwide outbreak of hepatitis A that peaked in 2009, by analyzing the results from a total of 424,245 anti-HAV sera from one central laboratory to which serologic tests for HAV were referred by medical institutions around the nation. The overall nationwide seroprevalence rates of anti-HAV gradually decreased during the last 10 years, from 65.6% to 62.2%, and age-specific seroprevalence showed dynamic changes. Seroprevalence continuously decreased in person aged 30 to 49 years due to the cohort effect; the segment of the population with natural HAV immunity was progressively replaced by birth cohorts with fewer early childhood HAV exposures and with no natural immunity. In contrast, it increased in persons aged 0 to 19 years during the 10-year period probably owing to vaccination. In persons aged 20 to 29 years, it reached a trough in 2010 and thereafter started to increase. This may have been influenced by both the cohort effect and vaccination. Therefore, in persons aged 20 to 39 years, the birth cohort born between the mid-1970s and mid-1990s and whose anti-HAV seroprevalence is still less than 50%, the risk of an HAV outbreak with clinically severe manifestations has increased.