Lu et al.1 document the waning of protective immunity to hepatitis B virus (HBV) in adolescents 15 years after receiving a plasma-derived hepatitis B vaccine manufactured in France, and they conclude that booster doses of the vaccine should be given. Levels of antibody to the hepatitis B surface antigen (anti-HBs) had fallen below the levels generally accepted as providing protection (≥10 mIU/mL) in 29.9% of subjects in a group of 78 children whose postvaccination anti-HBs had been documented. In a similar study,2 we documented the loss of protective anti-HBs in 33% of 101 children and adults 9 years after receiving a plasma-derived hepatitis B vaccine manufactured in the United States. Although the concordance of these results with two different plasma-derived hepatitis B vaccines (given in different concentrations on different dose schedules) might appear to justify extrapolation to recipients of other hepatitis B vaccines, this is not necessarily the case.
Plasma-derived hepatitis B vaccines were entirely displaced by recombinant hepatitis B vaccines in the 1990s. Some differences exist in the chemical structure of the hepatitis B surface antigen used to manufacture recombinant vaccines compared with that used to manufacture plasma-derived vaccines. In addition, the characteristics and durability of antibodies made in response to different vaccines can differ. Only follow-up studies of antibody persistence in recipients of recombinant hepatitis B vaccines can demonstrate whether booster doses should be recommended for those who were vaccinated with recombinant vaccines.