Hepatitis B Vaccines Clinical Trial
Official title:
Study of the Long Term Efficacy of Recombinant Hepatitis B Vaccine in Young Adults 20-22 Years After the Primary Vaccination in Nile Delta of Egypt
More than two billion individuals have serological evidence of hepatitis B virus (HBV)
infection worldwide. Of these, 240 million are chronic carriers and approximately 786,000
hepatitis B related deaths occur annually.
Currently available hepatitis B vaccines are extremely safe and have an efficacy of >90
percent against all HBV serotypes and genotypes. Thus, HBV infection can potentially be
eradicated through global vaccination. A positive immune response to the vaccine is defined
as the development of hepatitis B surface antibody (anti-HBs) at a titer of >10 mIU/mL.
Although anti-HBs titers decrease with time, the duration of protection is long. Protection
has been estimated to persist for up to 22 years after the primary vaccination schedule.
Protection from clinical disease, despite declining or even undetectable anti-HBs levels, is
probably due to the priming of memory cells, which are capable of eliciting an anamnestic
response when challenged. This is supported by the rapid increases in anti-HBs titers in
previously vaccinated individuals who administered booster injections.
A significant proportion of the vaccinated population loses both the protective levels of
anti-HBs and an anamnestic response. Recommendations for booster vaccination have been
proposed in a European consensus statement. Countries like the Netherlands, Germany, Spain,
France and Belgium recommend a booster dose depending on the post-vaccination anti-HBs
titer. In the UK, a single booster dose is recommended five years after primary vaccination.
In Egypt, the routine infant immunization for hepatitis B virus started in 1992, and was
given at 2nd, 4th and 6th months of age. In the present study the investigators will
investigate the long term efficacy of hepatitis B vaccination in young adults 20 to 22 years
after the primary vaccination in Nile Delta of Egypt.
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