- Category: HBV Vaccines
- Published on Friday, 15 November 2013 00:00
- Written by Liz Highleyman
Hepatitis B vaccination provides long-term protection through 30 years for a majority of recipients, and more than 90% were protected with either initial immunization or a booster, according to a presentation at the 64th AASLD Liver Meeting last week in Washington, DC.
Over years or decades, chronic hepatitis B virus (HBV) infection can lead to serious liver disease including cirrhosis and liver cancer. Hepatitis B is endemic in some parts of the world, especially in Asia and Africa, where it is often transmitted from mother-to-child. The widespread implementation of infant HBV vaccination, however, has reduced hepatitis B incidence in many countries worldwide.
Michael Bruce from the Centers for Disease Control and Prevention's Arctic Investigations Program presented long-term findings from the Alaska HBV Vaccine Demonstration Project, or Vax Demo. In the 1970s the Alaskan Native population had the highest rate of hepatitis B in the U.S. and one of the highest rates in the world, he noted as background.
Starting in 1981 the Vax Demo project immunized more than 1500 Yupik Eskimo children (age 6 months and older) and adults in 16 villages in western Alaska. Participants received 3 doses of the first commercially available HBV vaccine, made from inactivated virus obtained from plasma of infected individuals. In the late 1980s, this early vaccine was replaced with a safer recombinant or genetically engineered formulation (Merck's Recombivax).
Within 5 years after the start of the program, the incidence of symptomatic hepatitis B declined dramatically in the immunized population, from about 200 to less than 20 cases per 100,000 people.
Vax Demo researchers have followed this population for more than 30 years to determine how long vaccine protection lasts. Among 1530 children and adults who responded to the initial immunization series, a majority continued to have protective hepatitis B surface antibody (anti-HBs) levels of at least 10 mIU/mL:
- 5 years: 81%;
- 7 years: 74%;
- 15 years: 66%;
- 22 years: 60%.
At the 22-year follow-up -- which included a subset of vaccinated individuals in 7 villages -- people whose anti-HBs levels fell below 10 mIU/mL were given a 10 mcg Recombivax booster dose to test their immune response.
A total of 16 breakthrough HBV infections occurred, but there were no new breakthroughs after the 15-year follow-up. None of these infections were symptomatic and none become chronic.
The 30-year follow-up looked at residents of 13 villages who took 3 doses of the initial vaccine with documented response and received no additional boosters besides the 22-year follow-up dose. Again, a booster was administered to people who fell below the 10 mIU/mL threshold at the 30-year evaluation.
Vax Demo 30 included 435 eligible participants. Of these, 129 people did not get a booster at the 22-year follow-up, 63 people did receive the 22-year booster, and 243 people did not participate in Vax Demo 22.
- Overall, 219 participants, or 50%, still had anti-HBs levels of 10 mIU/mL or higher at 30 years.
- Sustained response rates were 66% for those without the 22-year booster, 14% for those who received the 22-year booster, and 51% for those who were not tested at 22 years.
- Again, no symptomatic acute or chronic HBV infections were identified at the 30-year follow-up.
- People who attained higher anti-HBs antibody levels after the initial vaccine series were more likely to still have protective levels at 30 years:
o 10-100 mIU/ml after primary series: 20% with sustained protective levels;
o 100-1000 mIU/ml: 34%;
o 1000-5000 mIU/ml: 58%;
o >5000 mIU/ml: 88%.
- Significant differences in sustained protection according to age were observed, but final data are not yet available, Bruce noted.
- There was no association between protective antibody levels and sex, body mass index, diabetes, cancer or use of immune-modulating drugs.
- Among people who had antibody levels below 10 mIU/mL and received a booster dose for the first time at 30 years, 92% who had adequate levels at year 22 and 88% who were not tested at year 22 achieved protective levels a month after boosting (people who received a booster at 22 years were not boosted again, even if their antibody levels remained low).
In summary, the researchers noted that antibody levels continued to decline over time, as did the proportion of participants with adequate levels, which fell from 81% at 5 years to 51% at 30 years. However, 88% of participants achieved adequate antibody levels after the 30-year booster.
"Overall, 94% had evidence of immunity" either with or without boosting, they stated. "Higher anti-HBs after primary series was associated with protective antibody levels at 30 years."
Based on these results, they concluded, "Protection by primary immunization with plasma-derived hep B vaccine lasts at least 30 years" and "booster doses [are] not needed."
Bruce said that these findings would likely also apply to people vaccinated with the current recombinant vaccine.
M Bruce, DJ Bruden, D Hurlburt, et al. Antibody Levels and Protection after Hepatitis B Vaccine: Results of a 30 year Follow-up Study and Response to a Booster Dose. 64th Annual Meeting of the American Association for the Study of Liver Diseases (AASLD 2013). Washington, DC, November 1-5, 2013. Abstract 187.