By Carol A. Kemper, MD, FACP
Source: McMahon BJ, et al. Antibody Levels and Protection After Hepatitis B Vaccination: Results of a 15-Year Follow-Up. Ann Intern Med. 2005;142:333-341.
The durability of hepatitis B vaccination has not been well delineated. While some experts recommend that health care workers receive a single booster vaccination at 8 to 10 years, there are no formal recommendations for this in the health care setting. Furthermore, the durability of vaccination in all these little kids now receiving vaccine is not known, and there are no guidelines for reassessment of titers or repeated vaccination later in life. Although one can measure persistence of anti-HBs antibody, the loss of detectable antibody (> 10 IU/L) over time does not necessarily imply loss of protection, as cellular immunity may provide a sufficiently protective role.
Longitudinal studies suggest that even when anti-HBs antibodies wane over time in heavily vaccinated populations, breakthrough infections are uncommon. McMahon and colleagues examined 1578 Alaskan natives who received 3 doses of HBV vaccine at the age of 6 months or older in 1981-1982. Slightly more than half (53%) were available for re-assessment 15 years later, during which mean plasma levels of anti-HBs decreased from an initial level of 872 IU/L to 27 IU/L. Higher levels of initial anti-HBs antibodies, male age, and age greater than 4 at the time of vaccination were associated with higher antibody levels 15 years later.
During the 15 years of follow-up, 16 documented and 8 possible breakthrough HBV infections occurred (1.26 per 1000 person-years), all of which were asymptomatic. Breakthrough infections were significantly more frequent in vaccine non-responders than responders. Interestingly, 2 persons were infected with wild type HBV and 4 were infected with wild type HBV and HbsAg variants.
Children who received HBV vaccine when they were less than 4 years had the fastest decline in antibody levels—meaning that just as they’ll be reaching their late teens and 20s, and becoming sexually active and potentially at risk for transmission of HBV—their titers will have waned. This leaves open the question of whether and when children vaccinated at a young age may require booster vaccination.
Carol A. Kemper, MD, FACP, is Clinical Associate Professor of Medicine at Stanford University and in the Division of Infectious Disease at Santa Clara Valley Medical Center.