Professor Moonkyung Jung, Department of Gastroenterology, Lifelong Health Promotion Center, Seoul St. Mary’s Hospital, Catholic University of Korea
Vaccination is recommended if there is no hepatitis A antibody after a health checkup, but many people do not think it is a big deal and do not get vaccinated. Hepatitis A is the most common cause, accounting for 70% of acute viral hepatitis in Korea. Hepatitis A is transmitted through the feces of a person infected with hepatitis A. It can be transmitted by eating water or food contaminated with feces, and can also be transmitted to others through hands contaminated with feces. In addition, as in 2019, seawater contaminated with a patient’s feces may condense the virus in shellfish and spread it through food. In addition, in the warm season, it is common to eat outside while doing a lot of outdoor activities. In this case, hepatitis A may increase significantly. As social distancing has recently been lifted due to the corona virus, the risk of infection has risen, so thorough infection prevention activities are essential.
Adults are more resilient and immune to most infectious diseases than children, but some viral diseases have more severe symptoms or more complications in adults than children, such as hepatitis A. Although spontaneous healing occurs without symptoms in childhood, symptoms develop in many cases in adulthood, fulminant liver failure occurs in less than 1% of cases, and, in rare cases, may develop to a situation requiring liver transplantation. Therefore, hepatitis A is a disease in which prevention rather than treatment after onset is very important for adults. The first to prevent hepatitis A is to thoroughly manage drinking water sources, food, and personal hygiene, and the second is to vaccinate against hepatitis A.
In Korea, as the hepatitis A vaccine changed to the national mandatory vaccination in 2015, the prevalence of hepatitis A antibodies in children and teenagers born after 2012 is high. On the other hand, those who were born between 1970 and 2000, that is, those in their 20s and 40s, especially those in their 20s and 30s, have a low rate of antibodies to hepatitis A at around 30%. This is because hepatitis A was not designated as a mandatory vaccination during infancy and infancy, and antibodies were not formed while growing up in a hygienic environment during childhood. Therefore, with the recent increase in hepatitis A, those in their 20s and 30s who have not received the vaccine since 2020 are also included in the vaccination recommendation, and it is recommended that those in their 40s or older be vaccinated when there is no antibody after performing a hepatitis A antibody test. . Theoretically, it is predicted that the preventive effect will be maintained for more than 25 years in adults and 10 to 14 years in children.
Since hepatitis A is a highly contagious virus, even healthy people who are not in high-risk groups are more likely to become infected without antibodies to hepatitis A, and the severity of symptoms tends to increase as the age of infection increases. Therefore, if there is no antibody because you have never been infected with hepatitis A and have not been vaccinated, or if the antibody disappears after receiving the vaccine, it is recommended to vaccinate again, so it is recommended to check the presence of antibodies. If there is no antibody after the hepatitis A antibody test, it is recommended to acquire immunity through two vaccinations 6 months apart. After vaccination, almost 100% of the hepatitis A virus antibody is produced, so there is no need to undergo an antibody test again.
Q1. Should people with hepatitis A get the hepatitis A vaccine?
If you get hepatitis A and then recover, you gain lifelong immunity. Therefore, a person who has been diagnosed with hepatitis A does not need a hepatitis A vaccine.
Q2. If I received the 1st dose of hepatitis A vaccine 3 years ago, I did not get the 2nd dose. In this case, should I get the 1st dose again?
Even if the second inoculation period (6 to 18 months after the first inoculation) is missed, only a set number of inoculations (two times) is required, and there is no need to inoculate again from the beginning. Therefore, if the second vaccination is delayed after the first vaccination of hepatitis A vaccine, only the second vaccination needs to be carried out as soon as possible.
Q3. If the second dose was accidentally administered 3 months after the first dose of hepatitis A vaccine, do I need to do the second dose again?
The minimum interval between vaccinations for hepatitis A vaccine is 6 months. Therefore, the second vaccination performed within 6 months is considered invalid, and the revaccination should be performed at least 6 months after the wrongly inoculated second vaccination.
Q4. I am planning a trip abroad to a country where hepatitis A is prevalent, so I want to get the hepatitis A vaccine. When should I vaccinate?
In principle, the hepatitis A vaccine should be administered twice at intervals of 6 to 18 months, but it is usually difficult to receive both doses prior to travel. However, since two doses of the hepatitis A vaccine are related to the duration of the antibody, it is possible to expect a preventive effect even with a single dose in this trip. In general, after a single hepatitis A vaccination, 50% of them develop antibodies after 2 weeks and 90% of them after 4 weeks. Therefore, the hepatitis A vaccine should be administered once at the time of this visit, and the second dose should be administered 6 to 18 months after the first dose after traveling.