Nationwide seroprevalence of hepatitis A in South Korea from 2009 to 2019

Abstract

Hepatitis A, an acute type of hepatitis caused by the hepatitis A virus, occurs worldwide. Following the 2009 hepatitis A epidemic in South Korea, patient outbreak reports were collectively converted to an "all-patient report" in 2011, and national immunization programs were introduced for children in 2015. In this study, we aimed to analyze the changes and characteristics of hepatitis A antibody titers in South Korea following the epidemic. The results of hepatitis A antibody tests performed at clinical laboratories from 2009 to 2019 were analyzed based on year, age, region, sex, and medical institution. The average 2009-2018 positive anti-hepatitis A virus immunoglobulin G rate was 51.8%, but it increased (56.06%) in 2019. Significantly different antibody-positive rates were observed based on age: <10 years, 54.5%; 20-29 years, 19.5%; ≥50 years, almost 100%. The positive rate of individuals in their teens and 20s gradually increased, whereas that of those in their 30s and 40s gradually decreased. Males had higher antibody-positive rates than females, and samples from higher-level general hospitals exhibited higher antibody rates. The positive anti-hepatitis A virus immunoglobulin M rates gradually decreased after 2009 and were <1% after 2012. However, a high positive rate of 3.69% was observed in 2019 when there was an epidemic. Anti-hepatitis A virus immunoglobulin G-positive rates were similar throughout the year, but the anti-hepatitis A virus immunoglobulin M-positive rates increased from January, peaked in April, and decreased from July, exhibiting distinct seasonality. This is considered to be related to groundwater pollution during the spring drought season. The introduction of the "all-patient report" and national vaccination program for children has had an effective influence on hepatitis A management. However, for hepatitis A prevention, policy considerations for high-risk age groups with low antibody-positive rates will be necessary.

Fig 1. 2009–2019 changes in the positive rate of hepatitis A antibody in South Korea, by age.

(A) Seroprevalence of anti-HAV IgG. (B) Seroprevalence of anti-HAV IgM. Over the 2009–2019 period, the positive rate of anti-HAV IgG antibodies in teenagers has been continuously increasing, whereas the positive rate of antibodies in individuals in their 40s has decreased. Antibody titers in their 20s and 30s gradually increased or decreased. However, there was no significant change compared with other age groups, and the antibody price was still low. In 2009, the anti-HAV IgM antibody showed high antibody titer, but gradually decreased and then increased suddenly in 2019. In 2009, high antibody titers were shown at all ages from teens to 40s. In particular, the IgM antibody value was high in individuals in their 20s and 30s. However, in 2019, 10 years later, high IgM antibody titers were observed in individuals in their 30s and 40s.

Fig 2. Regional anti-HAV IgM antibody-positive rate changes over 2009–2019.

Fig 3. Relationship between patient outbreak reports and anti-HAV IgM.

(A) Patient outbreak reports and anti-HAV IgM antibody-positive rates by year. (B) Monthly patient outbreak reports and anti-HAV IgM antibody-positive rates for 2019. The changes in the anti-HAV IgM antibody-positive rates and patient outbreak reports are similar since 2011 when the complete patient investigation began. From 2015, the trends in the two sets of data are consistent. However, in 2019, when there was an outbreak, the monthly patient report and the results of antibody levels from the five laboratories did not exactly match.

Fig 4. Seasonality of the anti-HAV antibody-positive rate.