Causes and countermeasures for repeated outbreaks of hepatitis A among adults in Korea

The 2019 hepatitis A outbreak has become increasingly prevalent among adults in Korea and is the largest outbreak since that in 2009-2010. The incidence in the current outbreak is highest among adults aged 35-44 years, corresponding to the peak incidence among those aged 25-34 years 10 years ago. This may indicate a cohort effect in the corresponding age group. Causes of these repeated outbreaks of hepatitis A in Korea are low level of immunity among adults, Korean food culture that consumes raw seafood such as salted clam and inadequate public health system. Among countermeasures, along with general infectious disease control measures including control of the infectious agent, infection spread, and host, urgent actions are needed to review the vaccination policy and establish an adequate public health system.