title: Nationwide Seropositivity of Hepatitis A in Republic of Korea from 2005 to 2014, before and after the Outbreak Peak in 2009.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Departments of Internal Medicine, Inje University Ilsan Paik Hospital, Goyang, Republic of Korea.
authors.forename: Kyung-Ah
authors.initials: KA
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, Seoul Clinical Laboratories, Yongin, Republic of Korea.
authors.forename: Anna
authors.initials: A
authors.lastname: Lee
authors.affiliation: Department of Cancer Control and Policy, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang, Republic of Korea.
authors.forename: Moran
authors.initials: M
authors.lastname: Ki
authors.affiliation: Departments of Internal Medicine, Seoul National University Bundang Hospital, College of Medicine, Seoul National University, Seongnam, Republic of Korea.
authors.forename: Sook-Hyang
authors.initials: SH
authors.lastname: Jeong
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D006506:Hepatitis A / Q000453:epidemiology*; D035922:Hepatitis A Antibodies / Q000097:blood*; D030041:Hepatitis A virus / Q000276:immunology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D056910:Republic of Korea / Q000453:epidemiology; D012189:Retrospective Studies; D016036:Seroepidemiologic Studies; D055815:Young Adult
chemical_list: D035922:Hepatitis A Antibodies