Zhao YL, et al. - Researchers sought to determine the effects of various types of hepatitis B vaccine (HepB) booster doses 2 to 32 years following primary immunization. Further, they examined the influencing factors, and proposed guidance concerning the necessity and timing of boosters. They enrolled 1,163 participants who were born from 1986 to 2015 and had received the HepB full-course primary vaccination; the participants were hepatitis B surface antigen (HBsAg) and hepatitis B core antibody negative and had hepatitis B surface antibody < 10 mIU/mL. Receipt of a single dose of HepB (CHO) and HepB (SC) was reported in 595 and 568 individuals, respectively. Using linear and logistic regression models, the factors associated with the immune response to booster vaccination were ascertained. A relatively higher seroconversion rate was evident among participants boostered with HepB (CHO) than those boostered with HepB (SC). As the two groups exhibit high seroconversion rates, the individuals remained protected despite low circulating antibodies, suggesting no urgent requirement for booster immunization. Factors contributing to lower responses to a booster dose were BMI ≥ 25 and prebooster anti-HBs concentration < 2.5 mIU/mL; these factors might indicate a greater risk of breakthrough infection.