The duration of protection afforded by hepatitis B vaccination is unknown.
Dr McMahon and colleagues conducted a prospective cohort study of 15 villages in southwest Alaska in1578 Alaska Natives vaccinated at age 6 months or older to determine antibody persistence and protection from Hepatitis B virus infection.
During 1981–1982, participants received 3 doses of plasma-derived Hepatitis B vaccine.
| Vaccination at age 6 months to 4 years afforded the lowest antibody to Hepatits B surface antigen levels|
|Annals of Internal Medicine|
The researchers followed up this cohort annually over the first 11 years, and tested 841 (53%) persons at 15 years.
The team tested antibody to Hepatitis B surface antigen, markers of Hepatitis B infection, and testing to identify Hepatitis B variants.
The research team observed that levels of antibodies to Hepatitis B surface antigen in the cohort decreased from a geometric mean concentration of 822 mIU/mL after vaccination to 27 mIU/mL at 15 years.
Initial levels of antibody to Hepatitis B surface antigen, older age at vaccination, and male sex were found to be associated with persistence of higher antibody levels at 15 years when analyzed by a longitudinal linear mixed model by the researchers.
After adjustment for initial antibody levels and sex, those vaccinated at age 6 months to 4 years had the lowest antibody to Hepatits B surface antigen levels at 15 years.
The researchers detected asymptomatic breakthrough infections in 16 participants and that these occurred more frequently in persons who did not respond to vaccination than those who responded.
In addition, the investigators noted that among infected persons with viremia, 2 were infected with wild-type Hepatitis B virus and 4 had Hepatitis B surface glycoprotein variants, generally accompanied by wild-type Hepatitis B.
The researchers reported a 47% loss of participants to follow-up at 15 years was but that characteristics of persons tested were similar to those of persons lost to follow-up.
Dr McMahon concludes, “Hepatitis B vaccination strongly protected against infection for at least 15 years in all age groups.”
“Antibody levels decreased the most among persons immunized at 4 years of age or younger.”