Hepatitis B core antibodies include core antibodies IgM and IgG. In chronic hepatitis B infection, there is not much difference between these two antibodies being positive or weakly positive. But if it is an acute hepatitis B infection, there is a difference. In the early stage of acute hepatitis B infection, IgM antibodies can be positive, but after entering the recovery period, the antibody value will gradually decline to weakly positive, and finally can turn negative. Therefore, the change from positive to weakly positive IgM in acute hepatitis B infection generally indicates that the virus is gradually clearing and the condition is improving. The opposite is true for IgM antibodies, which can be negative in the early stages of acute hepatitis B infection, gradually appearing weakly positive after entering the recovery period, and finally positive when the condition improves, so the two antibodies appear opposite.