If I am exposed to hepatitis B, how likely is it that it will become chronic? How hepatitis B affects each person is very complex, but in general, young children are much more likely to develop chronic hepatitis B once exposed. This table shows what is likely to happen, depending on how old you are when you are exposed to hepatitis B. Age exposed to hepatitis B Acute hepatitis B Chronic hepatitis B Infants (under 1 years old) Most will not get any acute hepatitis B symptoms 90% will get chronic (lifelong) hepatitis B Young children (aged 1 to 6 years old) Most will not get any acute hepatitis B symptoms 30% will get chronic (lifelong) hepatitis B Adults or older children (over 6 years old) Many will get acute hepatitis B symptoms Less than 5% will get chronic (lifelong) hepatitis B Find out more about hepatitis B vaccination References WHO. (2018, July 18). Hepatitis B. Retrieved from World Health Organization. Updated 11 December 2020