Hepatitis B vaccination is given in 3 doses, with the second and third doses given 1 month and 6 months after the first dose, respectively, hence the term “0-1-6 month immunization program. Why do we need 3 vaccinations? This is because more than half of the people who receive only one vaccination fail to produce antibodies to the hepatitis B virus – surface antibodies to the hepatitis B virus (abbreviated as anti-HBs) – and even for those who do, the amount of antibodies is very low, so they cannot effectively defend themselves against hepatitis B virus infection. After the 2nd vaccination, the number of people who produced antibodies increased to 70% and the amount of antibodies increased a bit, but this was not enough and a 3rd vaccination had to be received. After receiving the third immunization, more than 90% of the people are able to produce enough antibodies. Adequate antibody production is called an effective immune response (referred to as an effective response or normal response) by doctors. So how much antibody production is considered to have an effective or normal response? The serum anti-HBs (also known as the second of the five hepatitis B items) is tested one month after the full course of hepatitis B vaccination according to the 0-1-6 months immunization program, and an anti-HBs titer of ≥100 milliinternational units/ml (mIU/ml) is considered an effective or normal response; anti-HBs between 10 and 100 mIU/ml is considered a low response; anti-HBs <10 mIU/ml is considered a non-response. Low responders and non-responders after full hepatitis B vaccination have insufficient or no resistance to the hepatitis B virus and may still be infected with the hepatitis B virus.